intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

29 files changed, 10002 insertions, 0 deletions

diff --git a/contrib/tools/python3/src/Lib/email/__init__.py b/contrib/tools/python3/src/Lib/email/__init__.py
new file mode 100644
index 0000000000..fae872439e
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/__init__.py
@@ -0,0 +1,62 @@
+# Copyright (C) 2001-2007 Python Software Foundation
+# Author: Barry Warsaw
+# Contact: email-sig@python.org
+
+"""A package for parsing, handling, and generating email messages."""
+
+__all__ = [
+    'base64mime',
+    'charset',
+    'encoders',
+    'errors',
+    'feedparser',
+    'generator',
+    'header',
+    'iterators',
+    'message',
+    'message_from_file',
+    'message_from_binary_file',
+    'message_from_string',
+    'message_from_bytes',
+    'mime',
+    'parser',
+    'quoprimime',
+    'utils',
+    ]
+
+
+
+# Some convenience routines.  Don't import Parser and Message as side-effects
+# of importing email since those cascadingly import most of the rest of the
+# email package.
+def message_from_string(s, *args, **kws):
+    """Parse a string into a Message object model.
+
+    Optional _class and strict are passed to the Parser constructor.
+    """
+    from email.parser import Parser
+    return Parser(*args, **kws).parsestr(s)
+
+def message_from_bytes(s, *args, **kws):
+    """Parse a bytes string into a Message object model.
+
+    Optional _class and strict are passed to the Parser constructor.
+    """
+    from email.parser import BytesParser
+    return BytesParser(*args, **kws).parsebytes(s)
+
+def message_from_file(fp, *args, **kws):
+    """Read a file and parse its contents into a Message object model.
+
+    Optional _class and strict are passed to the Parser constructor.
+    """
+    from email.parser import Parser
+    return Parser(*args, **kws).parse(fp)
+
+def message_from_binary_file(fp, *args, **kws):
+    """Read a binary file and parse its contents into a Message object model.
+
+    Optional _class and strict are passed to the Parser constructor.
+    """
+    from email.parser import BytesParser
+    return BytesParser(*args, **kws).parse(fp)
diff --git a/contrib/tools/python3/src/Lib/email/_encoded_words.py b/contrib/tools/python3/src/Lib/email/_encoded_words.py
new file mode 100644
index 0000000000..295ae7eb21
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/_encoded_words.py
@@ -0,0 +1,233 @@
+""" Routines for manipulating RFC2047 encoded words.
+
+This is currently a package-private API, but will be considered for promotion
+to a public API if there is demand.
+
+"""
+
+# An ecoded word looks like this:
+#
+#        =?charset[*lang]?cte?encoded_string?=
+#
+# for more information about charset see the charset module.  Here it is one
+# of the preferred MIME charset names (hopefully; you never know when parsing).
+# cte (Content Transfer Encoding) is either 'q' or 'b' (ignoring case).  In
+# theory other letters could be used for other encodings, but in practice this
+# (almost?) never happens.  There could be a public API for adding entries
+# to the CTE tables, but YAGNI for now.  'q' is Quoted Printable, 'b' is
+# Base64.  The meaning of encoded_string should be obvious.  'lang' is optional
+# as indicated by the brackets (they are not part of the syntax) but is almost
+# never encountered in practice.
+#
+# The general interface for a CTE decoder is that it takes the encoded_string
+# as its argument, and returns a tuple (cte_decoded_string, defects).  The
+# cte_decoded_string is the original binary that was encoded using the
+# specified cte.  'defects' is a list of MessageDefect instances indicating any
+# problems encountered during conversion.  'charset' and 'lang' are the
+# corresponding strings extracted from the EW, case preserved.
+#
+# The general interface for a CTE encoder is that it takes a binary sequence
+# as input and returns the cte_encoded_string, which is an ascii-only string.
+#
+# Each decoder must also supply a length function that takes the binary
+# sequence as its argument and returns the length of the resulting encoded
+# string.
+#
+# The main API functions for the module are decode, which calls the decoder
+# referenced by the cte specifier, and encode, which adds the appropriate
+# RFC 2047 "chrome" to the encoded string, and can optionally automatically
+# select the shortest possible encoding.  See their docstrings below for
+# details.
+
+import re
+import base64
+import binascii
+import functools
+from string import ascii_letters, digits
+from email import errors
+
+__all__ = ['decode_q',
+           'encode_q',
+           'decode_b',
+           'encode_b',
+           'len_q',
+           'len_b',
+           'decode',
+           'encode',
+           ]
+
+#
+# Quoted Printable
+#
+
+# regex based decoder.
+_q_byte_subber = functools.partial(re.compile(br'=([a-fA-F0-9]{2})').sub,
+        lambda m: bytes.fromhex(m.group(1).decode()))
+
+def decode_q(encoded):
+    encoded = encoded.replace(b'_', b' ')
+    return _q_byte_subber(encoded), []
+
+
+# dict mapping bytes to their encoded form
+class _QByteMap(dict):
+
+    safe = b'-!*+/' + ascii_letters.encode('ascii') + digits.encode('ascii')
+
+    def __missing__(self, key):
+        if key in self.safe:
+            self[key] = chr(key)
+        else:
+            self[key] = "={:02X}".format(key)
+        return self[key]
+
+_q_byte_map = _QByteMap()
+
+# In headers spaces are mapped to '_'.
+_q_byte_map[ord(' ')] = '_'
+
+def encode_q(bstring):
+    return ''.join(_q_byte_map[x] for x in bstring)
+
+def len_q(bstring):
+    return sum(len(_q_byte_map[x]) for x in bstring)
+
+
+#
+# Base64
+#
+
+def decode_b(encoded):
+    # First try encoding with validate=True, fixing the padding if needed.
+    # This will succeed only if encoded includes no invalid characters.
+    pad_err = len(encoded) % 4
+    missing_padding = b'==='[:4-pad_err] if pad_err else b''
+    try:
+        return (
+            base64.b64decode(encoded + missing_padding, validate=True),
+            [errors.InvalidBase64PaddingDefect()] if pad_err else [],
+        )
+    except binascii.Error:
+        # Since we had correct padding, this is likely an invalid char error.
+        #
+        # The non-alphabet characters are ignored as far as padding
+        # goes, but we don't know how many there are.  So try without adding
+        # padding to see if it works.
+        try:
+            return (
+                base64.b64decode(encoded, validate=False),
+                [errors.InvalidBase64CharactersDefect()],
+            )
+        except binascii.Error:
+            # Add as much padding as could possibly be necessary (extra padding
+            # is ignored).
+            try:
+                return (
+                    base64.b64decode(encoded + b'==', validate=False),
+                    [errors.InvalidBase64CharactersDefect(),
+                     errors.InvalidBase64PaddingDefect()],
+                )
+            except binascii.Error:
+                # This only happens when the encoded string's length is 1 more
+                # than a multiple of 4, which is invalid.
+                #
+                # bpo-27397: Just return the encoded string since there's no
+                # way to decode.
+                return encoded, [errors.InvalidBase64LengthDefect()]
+
+def encode_b(bstring):
+    return base64.b64encode(bstring).decode('ascii')
+
+def len_b(bstring):
+    groups_of_3, leftover = divmod(len(bstring), 3)
+    # 4 bytes out for each 3 bytes (or nonzero fraction thereof) in.
+    return groups_of_3 * 4 + (4 if leftover else 0)
+
+
+_cte_decoders = {
+    'q': decode_q,
+    'b': decode_b,
+    }
+
+def decode(ew):
+    """Decode encoded word and return (string, charset, lang, defects) tuple.
+
+    An RFC 2047/2243 encoded word has the form:
+
+        =?charset*lang?cte?encoded_string?=
+
+    where '*lang' may be omitted but the other parts may not be.
+
+    This function expects exactly such a string (that is, it does not check the
+    syntax and may raise errors if the string is not well formed), and returns
+    the encoded_string decoded first from its Content Transfer Encoding and
+    then from the resulting bytes into unicode using the specified charset.  If
+    the cte-decoded string does not successfully decode using the specified
+    character set, a defect is added to the defects list and the unknown octets
+    are replaced by the unicode 'unknown' character \\uFDFF.
+
+    The specified charset and language are returned.  The default for language,
+    which is rarely if ever encountered, is the empty string.
+
+    """
+    _, charset, cte, cte_string, _ = ew.split('?')
+    charset, _, lang = charset.partition('*')
+    cte = cte.lower()
+    # Recover the original bytes and do CTE decoding.
+    bstring = cte_string.encode('ascii', 'surrogateescape')
+    bstring, defects = _cte_decoders[cte](bstring)
+    # Turn the CTE decoded bytes into unicode.
+    try:
+        string = bstring.decode(charset)
+    except UnicodeError:
+        defects.append(errors.UndecodableBytesDefect("Encoded word "
+            "contains bytes not decodable using {} charset".format(charset)))
+        string = bstring.decode(charset, 'surrogateescape')
+    except LookupError:
+        string = bstring.decode('ascii', 'surrogateescape')
+        if charset.lower() != 'unknown-8bit':
+            defects.append(errors.CharsetError("Unknown charset {} "
+                "in encoded word; decoded as unknown bytes".format(charset)))
+    return string, charset, lang, defects
+
+
+_cte_encoders = {
+    'q': encode_q,
+    'b': encode_b,
+    }
+
+_cte_encode_length = {
+    'q': len_q,
+    'b': len_b,
+    }
+
+def encode(string, charset='utf-8', encoding=None, lang=''):
+    """Encode string using the CTE encoding that produces the shorter result.
+
+    Produces an RFC 2047/2243 encoded word of the form:
+
+        =?charset*lang?cte?encoded_string?=
+
+    where '*lang' is omitted unless the 'lang' parameter is given a value.
+    Optional argument charset (defaults to utf-8) specifies the charset to use
+    to encode the string to binary before CTE encoding it.  Optional argument
+    'encoding' is the cte specifier for the encoding that should be used ('q'
+    or 'b'); if it is None (the default) the encoding which produces the
+    shortest encoded sequence is used, except that 'q' is preferred if it is up
+    to five characters longer.  Optional argument 'lang' (default '') gives the
+    RFC 2243 language string to specify in the encoded word.
+
+    """
+    if charset == 'unknown-8bit':
+        bstring = string.encode('ascii', 'surrogateescape')
+    else:
+        bstring = string.encode(charset)
+    if encoding is None:
+        qlen = _cte_encode_length['q'](bstring)
+        blen = _cte_encode_length['b'](bstring)
+        # Bias toward q.  5 is arbitrary.
+        encoding = 'q' if qlen - blen < 5 else 'b'
+    encoded = _cte_encoders[encoding](bstring)
+    if lang:
+        lang = '*' + lang
+    return "=?{}{}?{}?{}?=".format(charset, lang, encoding, encoded)
diff --git a/contrib/tools/python3/src/Lib/email/_header_value_parser.py b/contrib/tools/python3/src/Lib/email/_header_value_parser.py
new file mode 100644
index 0000000000..51d355fbb0
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/_header_value_parser.py
@@ -0,0 +1,3003 @@
+"""Header value parser implementing various email-related RFC parsing rules.
+
+The parsing methods defined in this module implement various email related
+parsing rules.  Principal among them is RFC 5322, which is the followon
+to RFC 2822 and primarily a clarification of the former.  It also implements
+RFC 2047 encoded word decoding.
+
+RFC 5322 goes to considerable trouble to maintain backward compatibility with
+RFC 822 in the parse phase, while cleaning up the structure on the generation
+phase.  This parser supports correct RFC 5322 generation by tagging white space
+as folding white space only when folding is allowed in the non-obsolete rule
+sets.  Actually, the parser is even more generous when accepting input than RFC
+5322 mandates, following the spirit of Postel's Law, which RFC 5322 encourages.
+Where possible deviations from the standard are annotated on the 'defects'
+attribute of tokens that deviate.
+
+The general structure of the parser follows RFC 5322, and uses its terminology
+where there is a direct correspondence.  Where the implementation requires a
+somewhat different structure than that used by the formal grammar, new terms
+that mimic the closest existing terms are used.  Thus, it really helps to have
+a copy of RFC 5322 handy when studying this code.
+
+Input to the parser is a string that has already been unfolded according to
+RFC 5322 rules.  According to the RFC this unfolding is the very first step, and
+this parser leaves the unfolding step to a higher level message parser, which
+will have already detected the line breaks that need unfolding while
+determining the beginning and end of each header.
+
+The output of the parser is a TokenList object, which is a list subclass.  A
+TokenList is a recursive data structure.  The terminal nodes of the structure
+are Terminal objects, which are subclasses of str.  These do not correspond
+directly to terminal objects in the formal grammar, but are instead more
+practical higher level combinations of true terminals.
+
+All TokenList and Terminal objects have a 'value' attribute, which produces the
+semantically meaningful value of that part of the parse subtree.  The value of
+all whitespace tokens (no matter how many sub-tokens they may contain) is a
+single space, as per the RFC rules.  This includes 'CFWS', which is herein
+included in the general class of whitespace tokens.  There is one exception to
+the rule that whitespace tokens are collapsed into single spaces in values: in
+the value of a 'bare-quoted-string' (a quoted-string with no leading or
+trailing whitespace), any whitespace that appeared between the quotation marks
+is preserved in the returned value.  Note that in all Terminal strings quoted
+pairs are turned into their unquoted values.
+
+All TokenList and Terminal objects also have a string value, which attempts to
+be a "canonical" representation of the RFC-compliant form of the substring that
+produced the parsed subtree, including minimal use of quoted pair quoting.
+Whitespace runs are not collapsed.
+
+Comment tokens also have a 'content' attribute providing the string found
+between the parens (including any nested comments) with whitespace preserved.
+
+All TokenList and Terminal objects have a 'defects' attribute which is a
+possibly empty list all of the defects found while creating the token.  Defects
+may appear on any token in the tree, and a composite list of all defects in the
+subtree is available through the 'all_defects' attribute of any node.  (For
+Terminal notes x.defects == x.all_defects.)
+
+Each object in a parse tree is called a 'token', and each has a 'token_type'
+attribute that gives the name from the RFC 5322 grammar that it represents.
+Not all RFC 5322 nodes are produced, and there is one non-RFC 5322 node that
+may be produced: 'ptext'.  A 'ptext' is a string of printable ascii characters.
+It is returned in place of lists of (ctext/quoted-pair) and
+(qtext/quoted-pair).
+
+XXX: provide complete list of token types.
+"""
+
+import re
+import sys
+import urllib   # For urllib.parse.unquote
+from string import hexdigits
+from operator import itemgetter
+from email import _encoded_words as _ew
+from email import errors
+from email import utils
+
+#
+# Useful constants and functions
+#
+
+WSP = set(' \t')
+CFWS_LEADER = WSP | set('(')
+SPECIALS = set(r'()<>@,:;.\"[]')
+ATOM_ENDS = SPECIALS | WSP
+DOT_ATOM_ENDS = ATOM_ENDS - set('.')
+# '.', '"', and '(' do not end phrases in order to support obs-phrase
+PHRASE_ENDS = SPECIALS - set('."(')
+TSPECIALS = (SPECIALS | set('/?=')) - set('.')
+TOKEN_ENDS = TSPECIALS | WSP
+ASPECIALS = TSPECIALS | set("*'%")
+ATTRIBUTE_ENDS = ASPECIALS | WSP
+EXTENDED_ATTRIBUTE_ENDS = ATTRIBUTE_ENDS - set('%')
+
+def quote_string(value):
+    return '"'+str(value).replace('\\', '\\\\').replace('"', r'\"')+'"'
+
+# Match a RFC 2047 word, looks like =?utf-8?q?someword?=
+rfc2047_matcher = re.compile(r'''
+   =\?            # literal =?
+   [^?]*          # charset
+   \?             # literal ?
+   [qQbB]         # literal 'q' or 'b', case insensitive
+   \?             # literal ?
+  .*?             # encoded word
+  \?=             # literal ?=
+''', re.VERBOSE | re.MULTILINE)
+
+
+#
+# TokenList and its subclasses
+#
+
+class TokenList(list):
+
+    token_type = None
+    syntactic_break = True
+    ew_combine_allowed = True
+
+    def __init__(self, *args, **kw):
+        super().__init__(*args, **kw)
+        self.defects = []
+
+    def __str__(self):
+        return ''.join(str(x) for x in self)
+
+    def __repr__(self):
+        return '{}({})'.format(self.__class__.__name__,
+                             super().__repr__())
+
+    @property
+    def value(self):
+        return ''.join(x.value for x in self if x.value)
+
+    @property
+    def all_defects(self):
+        return sum((x.all_defects for x in self), self.defects)
+
+    def startswith_fws(self):
+        return self[0].startswith_fws()
+
+    @property
+    def as_ew_allowed(self):
+        """True if all top level tokens of this part may be RFC2047 encoded."""
+        return all(part.as_ew_allowed for part in self)
+
+    @property
+    def comments(self):
+        comments = []
+        for token in self:
+            comments.extend(token.comments)
+        return comments
+
+    def fold(self, *, policy):
+        return _refold_parse_tree(self, policy=policy)
+
+    def pprint(self, indent=''):
+        print(self.ppstr(indent=indent))
+
+    def ppstr(self, indent=''):
+        return '\n'.join(self._pp(indent=indent))
+
+    def _pp(self, indent=''):
+        yield '{}{}/{}('.format(
+            indent,
+            self.__class__.__name__,
+            self.token_type)
+        for token in self:
+            if not hasattr(token, '_pp'):
+                yield (indent + '    !! invalid element in token '
+                                        'list: {!r}'.format(token))
+            else:
+                yield from token._pp(indent+'    ')
+        if self.defects:
+            extra = ' Defects: {}'.format(self.defects)
+        else:
+            extra = ''
+        yield '{}){}'.format(indent, extra)
+
+
+class WhiteSpaceTokenList(TokenList):
+
+    @property
+    def value(self):
+        return ' '
+
+    @property
+    def comments(self):
+        return [x.content for x in self if x.token_type=='comment']
+
+
+class UnstructuredTokenList(TokenList):
+    token_type = 'unstructured'
+
+
+class Phrase(TokenList):
+    token_type = 'phrase'
+
+class Word(TokenList):
+    token_type = 'word'
+
+
+class CFWSList(WhiteSpaceTokenList):
+    token_type = 'cfws'
+
+
+class Atom(TokenList):
+    token_type = 'atom'
+
+
+class Token(TokenList):
+    token_type = 'token'
+    encode_as_ew = False
+
+
+class EncodedWord(TokenList):
+    token_type = 'encoded-word'
+    cte = None
+    charset = None
+    lang = None
+
+
+class QuotedString(TokenList):
+
+    token_type = 'quoted-string'
+
+    @property
+    def content(self):
+        for x in self:
+            if x.token_type == 'bare-quoted-string':
+                return x.value
+
+    @property
+    def quoted_value(self):
+        res = []
+        for x in self:
+            if x.token_type == 'bare-quoted-string':
+                res.append(str(x))
+            else:
+                res.append(x.value)
+        return ''.join(res)
+
+    @property
+    def stripped_value(self):
+        for token in self:
+            if token.token_type == 'bare-quoted-string':
+                return token.value
+
+
+class BareQuotedString(QuotedString):
+
+    token_type = 'bare-quoted-string'
+
+    def __str__(self):
+        return quote_string(''.join(str(x) for x in self))
+
+    @property
+    def value(self):
+        return ''.join(str(x) for x in self)
+
+
+class Comment(WhiteSpaceTokenList):
+
+    token_type = 'comment'
+
+    def __str__(self):
+        return ''.join(sum([
+                            ["("],
+                            [self.quote(x) for x in self],
+                            [")"],
+                            ], []))
+
+    def quote(self, value):
+        if value.token_type == 'comment':
+            return str(value)
+        return str(value).replace('\\', '\\\\').replace(
+                                  '(', r'\(').replace(
+                                  ')', r'\)')
+
+    @property
+    def content(self):
+        return ''.join(str(x) for x in self)
+
+    @property
+    def comments(self):
+        return [self.content]
+
+class AddressList(TokenList):
+
+    token_type = 'address-list'
+
+    @property
+    def addresses(self):
+        return [x for x in self if x.token_type=='address']
+
+    @property
+    def mailboxes(self):
+        return sum((x.mailboxes
+                    for x in self if x.token_type=='address'), [])
+
+    @property
+    def all_mailboxes(self):
+        return sum((x.all_mailboxes
+                    for x in self if x.token_type=='address'), [])
+
+
+class Address(TokenList):
+
+    token_type = 'address'
+
+    @property
+    def display_name(self):
+        if self[0].token_type == 'group':
+            return self[0].display_name
+
+    @property
+    def mailboxes(self):
+        if self[0].token_type == 'mailbox':
+            return [self[0]]
+        elif self[0].token_type == 'invalid-mailbox':
+            return []
+        return self[0].mailboxes
+
+    @property
+    def all_mailboxes(self):
+        if self[0].token_type == 'mailbox':
+            return [self[0]]
+        elif self[0].token_type == 'invalid-mailbox':
+            return [self[0]]
+        return self[0].all_mailboxes
+
+class MailboxList(TokenList):
+
+    token_type = 'mailbox-list'
+
+    @property
+    def mailboxes(self):
+        return [x for x in self if x.token_type=='mailbox']
+
+    @property
+    def all_mailboxes(self):
+        return [x for x in self
+            if x.token_type in ('mailbox', 'invalid-mailbox')]
+
+
+class GroupList(TokenList):
+
+    token_type = 'group-list'
+
+    @property
+    def mailboxes(self):
+        if not self or self[0].token_type != 'mailbox-list':
+            return []
+        return self[0].mailboxes
+
+    @property
+    def all_mailboxes(self):
+        if not self or self[0].token_type != 'mailbox-list':
+            return []
+        return self[0].all_mailboxes
+
+
+class Group(TokenList):
+
+    token_type = "group"
+
+    @property
+    def mailboxes(self):
+        if self[2].token_type != 'group-list':
+            return []
+        return self[2].mailboxes
+
+    @property
+    def all_mailboxes(self):
+        if self[2].token_type != 'group-list':
+            return []
+        return self[2].all_mailboxes
+
+    @property
+    def display_name(self):
+        return self[0].display_name
+
+
+class NameAddr(TokenList):
+
+    token_type = 'name-addr'
+
+    @property
+    def display_name(self):
+        if len(self) == 1:
+            return None
+        return self[0].display_name
+
+    @property
+    def local_part(self):
+        return self[-1].local_part
+
+    @property
+    def domain(self):
+        return self[-1].domain
+
+    @property
+    def route(self):
+        return self[-1].route
+
+    @property
+    def addr_spec(self):
+        return self[-1].addr_spec
+
+
+class AngleAddr(TokenList):
+
+    token_type = 'angle-addr'
+
+    @property
+    def local_part(self):
+        for x in self:
+            if x.token_type == 'addr-spec':
+                return x.local_part
+
+    @property
+    def domain(self):
+        for x in self:
+            if x.token_type == 'addr-spec':
+                return x.domain
+
+    @property
+    def route(self):
+        for x in self:
+            if x.token_type == 'obs-route':
+                return x.domains
+
+    @property
+    def addr_spec(self):
+        for x in self:
+            if x.token_type == 'addr-spec':
+                if x.local_part:
+                    return x.addr_spec
+                else:
+                    return quote_string(x.local_part) + x.addr_spec
+        else:
+            return '<>'
+
+
+class ObsRoute(TokenList):
+
+    token_type = 'obs-route'
+
+    @property
+    def domains(self):
+        return [x.domain for x in self if x.token_type == 'domain']
+
+
+class Mailbox(TokenList):
+
+    token_type = 'mailbox'
+
+    @property
+    def display_name(self):
+        if self[0].token_type == 'name-addr':
+            return self[0].display_name
+
+    @property
+    def local_part(self):
+        return self[0].local_part
+
+    @property
+    def domain(self):
+        return self[0].domain
+
+    @property
+    def route(self):
+        if self[0].token_type == 'name-addr':
+            return self[0].route
+
+    @property
+    def addr_spec(self):
+        return self[0].addr_spec
+
+
+class InvalidMailbox(TokenList):
+
+    token_type = 'invalid-mailbox'
+
+    @property
+    def display_name(self):
+        return None
+
+    local_part = domain = route = addr_spec = display_name
+
+
+class Domain(TokenList):
+
+    token_type = 'domain'
+    as_ew_allowed = False
+
+    @property
+    def domain(self):
+        return ''.join(super().value.split())
+
+
+class DotAtom(TokenList):
+    token_type = 'dot-atom'
+
+
+class DotAtomText(TokenList):
+    token_type = 'dot-atom-text'
+    as_ew_allowed = True
+
+
+class NoFoldLiteral(TokenList):
+    token_type = 'no-fold-literal'
+    as_ew_allowed = False
+
+
+class AddrSpec(TokenList):
+
+    token_type = 'addr-spec'
+    as_ew_allowed = False
+
+    @property
+    def local_part(self):
+        return self[0].local_part
+
+    @property
+    def domain(self):
+        if len(self) < 3:
+            return None
+        return self[-1].domain
+
+    @property
+    def value(self):
+        if len(self) < 3:
+            return self[0].value
+        return self[0].value.rstrip()+self[1].value+self[2].value.lstrip()
+
+    @property
+    def addr_spec(self):
+        nameset = set(self.local_part)
+        if len(nameset) > len(nameset-DOT_ATOM_ENDS):
+            lp = quote_string(self.local_part)
+        else:
+            lp = self.local_part
+        if self.domain is not None:
+            return lp + '@' + self.domain
+        return lp
+
+
+class ObsLocalPart(TokenList):
+
+    token_type = 'obs-local-part'
+    as_ew_allowed = False
+
+
+class DisplayName(Phrase):
+
+    token_type = 'display-name'
+    ew_combine_allowed = False
+
+    @property
+    def display_name(self):
+        res = TokenList(self)
+        if len(res) == 0:
+            return res.value
+        if res[0].token_type == 'cfws':
+            res.pop(0)
+        else:
+            if res[0][0].token_type == 'cfws':
+                res[0] = TokenList(res[0][1:])
+        if res[-1].token_type == 'cfws':
+            res.pop()
+        else:
+            if res[-1][-1].token_type == 'cfws':
+                res[-1] = TokenList(res[-1][:-1])
+        return res.value
+
+    @property
+    def value(self):
+        quote = False
+        if self.defects:
+            quote = True
+        else:
+            for x in self:
+                if x.token_type == 'quoted-string':
+                    quote = True
+        if len(self) != 0 and quote:
+            pre = post = ''
+            if self[0].token_type=='cfws' or self[0][0].token_type=='cfws':
+                pre = ' '
+            if self[-1].token_type=='cfws' or self[-1][-1].token_type=='cfws':
+                post = ' '
+            return pre+quote_string(self.display_name)+post
+        else:
+            return super().value
+
+
+class LocalPart(TokenList):
+
+    token_type = 'local-part'
+    as_ew_allowed = False
+
+    @property
+    def value(self):
+        if self[0].token_type == "quoted-string":
+            return self[0].quoted_value
+        else:
+            return self[0].value
+
+    @property
+    def local_part(self):
+        # Strip whitespace from front, back, and around dots.
+        res = [DOT]
+        last = DOT
+        last_is_tl = False
+        for tok in self[0] + [DOT]:
+            if tok.token_type == 'cfws':
+                continue
+            if (last_is_tl and tok.token_type == 'dot' and
+                    last[-1].token_type == 'cfws'):
+                res[-1] = TokenList(last[:-1])
+            is_tl = isinstance(tok, TokenList)
+            if (is_tl and last.token_type == 'dot' and
+                    tok[0].token_type == 'cfws'):
+                res.append(TokenList(tok[1:]))
+            else:
+                res.append(tok)
+            last = res[-1]
+            last_is_tl = is_tl
+        res = TokenList(res[1:-1])
+        return res.value
+
+
+class DomainLiteral(TokenList):
+
+    token_type = 'domain-literal'
+    as_ew_allowed = False
+
+    @property
+    def domain(self):
+        return ''.join(super().value.split())
+
+    @property
+    def ip(self):
+        for x in self:
+            if x.token_type == 'ptext':
+                return x.value
+
+
+class MIMEVersion(TokenList):
+
+    token_type = 'mime-version'
+    major = None
+    minor = None
+
+
+class Parameter(TokenList):
+
+    token_type = 'parameter'
+    sectioned = False
+    extended = False
+    charset = 'us-ascii'
+
+    @property
+    def section_number(self):
+        # Because the first token, the attribute (name) eats CFWS, the second
+        # token is always the section if there is one.
+        return self[1].number if self.sectioned else 0
+
+    @property
+    def param_value(self):
+        # This is part of the "handle quoted extended parameters" hack.
+        for token in self:
+            if token.token_type == 'value':
+                return token.stripped_value
+            if token.token_type == 'quoted-string':
+                for token in token:
+                    if token.token_type == 'bare-quoted-string':
+                        for token in token:
+                            if token.token_type == 'value':
+                                return token.stripped_value
+        return ''
+
+
+class InvalidParameter(Parameter):
+
+    token_type = 'invalid-parameter'
+
+
+class Attribute(TokenList):
+
+    token_type = 'attribute'
+
+    @property
+    def stripped_value(self):
+        for token in self:
+            if token.token_type.endswith('attrtext'):
+                return token.value
+
+class Section(TokenList):
+
+    token_type = 'section'
+    number = None
+
+
+class Value(TokenList):
+
+    token_type = 'value'
+
+    @property
+    def stripped_value(self):
+        token = self[0]
+        if token.token_type == 'cfws':
+            token = self[1]
+        if token.token_type.endswith(
+                ('quoted-string', 'attribute', 'extended-attribute')):
+            return token.stripped_value
+        return self.value
+
+
+class MimeParameters(TokenList):
+
+    token_type = 'mime-parameters'
+    syntactic_break = False
+
+    @property
+    def params(self):
+        # The RFC specifically states that the ordering of parameters is not
+        # guaranteed and may be reordered by the transport layer.  So we have
+        # to assume the RFC 2231 pieces can come in any order.  However, we
+        # output them in the order that we first see a given name, which gives
+        # us a stable __str__.
+        params = {}  # Using order preserving dict from Python 3.7+
+        for token in self:
+            if not token.token_type.endswith('parameter'):
+                continue
+            if token[0].token_type != 'attribute':
+                continue
+            name = token[0].value.strip()
+            if name not in params:
+                params[name] = []
+            params[name].append((token.section_number, token))
+        for name, parts in params.items():
+            parts = sorted(parts, key=itemgetter(0))
+            first_param = parts[0][1]
+            charset = first_param.charset
+            # Our arbitrary error recovery is to ignore duplicate parameters,
+            # to use appearance order if there are duplicate rfc 2231 parts,
+            # and to ignore gaps.  This mimics the error recovery of get_param.
+            if not first_param.extended and len(parts) > 1:
+                if parts[1][0] == 0:
+                    parts[1][1].defects.append(errors.InvalidHeaderDefect(
+                        'duplicate parameter name; duplicate(s) ignored'))
+                    parts = parts[:1]
+                # Else assume the *0* was missing...note that this is different
+                # from get_param, but we registered a defect for this earlier.
+            value_parts = []
+            i = 0
+            for section_number, param in parts:
+                if section_number != i:
+                    # We could get fancier here and look for a complete
+                    # duplicate extended parameter and ignore the second one
+                    # seen.  But we're not doing that.  The old code didn't.
+                    if not param.extended:
+                        param.defects.append(errors.InvalidHeaderDefect(
+                            'duplicate parameter name; duplicate ignored'))
+                        continue
+                    else:
+                        param.defects.append(errors.InvalidHeaderDefect(
+                            "inconsistent RFC2231 parameter numbering"))
+                i += 1
+                value = param.param_value
+                if param.extended:
+                    try:
+                        value = urllib.parse.unquote_to_bytes(value)
+                    except UnicodeEncodeError:
+                        # source had surrogate escaped bytes.  What we do now
+                        # is a bit of an open question.  I'm not sure this is
+                        # the best choice, but it is what the old algorithm did
+                        value = urllib.parse.unquote(value, encoding='latin-1')
+                    else:
+                        try:
+                            value = value.decode(charset, 'surrogateescape')
+                        except LookupError:
+                            # XXX: there should really be a custom defect for
+                            # unknown character set to make it easy to find,
+                            # because otherwise unknown charset is a silent
+                            # failure.
+                            value = value.decode('us-ascii', 'surrogateescape')
+                        if utils._has_surrogates(value):
+                            param.defects.append(errors.UndecodableBytesDefect())
+                value_parts.append(value)
+            value = ''.join(value_parts)
+            yield name, value
+
+    def __str__(self):
+        params = []
+        for name, value in self.params:
+            if value:
+                params.append('{}={}'.format(name, quote_string(value)))
+            else:
+                params.append(name)
+        params = '; '.join(params)
+        return ' ' + params if params else ''
+
+
+class ParameterizedHeaderValue(TokenList):
+
+    # Set this false so that the value doesn't wind up on a new line even
+    # if it and the parameters would fit there but not on the first line.
+    syntactic_break = False
+
+    @property
+    def params(self):
+        for token in reversed(self):
+            if token.token_type == 'mime-parameters':
+                return token.params
+        return {}
+
+
+class ContentType(ParameterizedHeaderValue):
+    token_type = 'content-type'
+    as_ew_allowed = False
+    maintype = 'text'
+    subtype = 'plain'
+
+
+class ContentDisposition(ParameterizedHeaderValue):
+    token_type = 'content-disposition'
+    as_ew_allowed = False
+    content_disposition = None
+
+
+class ContentTransferEncoding(TokenList):
+    token_type = 'content-transfer-encoding'
+    as_ew_allowed = False
+    cte = '7bit'
+
+
+class HeaderLabel(TokenList):
+    token_type = 'header-label'
+    as_ew_allowed = False
+
+
+class MsgID(TokenList):
+    token_type = 'msg-id'
+    as_ew_allowed = False
+
+    def fold(self, policy):
+        # message-id tokens may not be folded.
+        return str(self) + policy.linesep
+
+
+class MessageID(MsgID):
+    token_type = 'message-id'
+
+
+class InvalidMessageID(MessageID):
+    token_type = 'invalid-message-id'
+
+
+class Header(TokenList):
+    token_type = 'header'
+
+
+#
+# Terminal classes and instances
+#
+
+class Terminal(str):
+
+    as_ew_allowed = True
+    ew_combine_allowed = True
+    syntactic_break = True
+
+    def __new__(cls, value, token_type):
+        self = super().__new__(cls, value)
+        self.token_type = token_type
+        self.defects = []
+        return self
+
+    def __repr__(self):
+        return "{}({})".format(self.__class__.__name__, super().__repr__())
+
+    def pprint(self):
+        print(self.__class__.__name__ + '/' + self.token_type)
+
+    @property
+    def all_defects(self):
+        return list(self.defects)
+
+    def _pp(self, indent=''):
+        return ["{}{}/{}({}){}".format(
+            indent,
+            self.__class__.__name__,
+            self.token_type,
+            super().__repr__(),
+            '' if not self.defects else ' {}'.format(self.defects),
+            )]
+
+    def pop_trailing_ws(self):
+        # This terminates the recursion.
+        return None
+
+    @property
+    def comments(self):
+        return []
+
+    def __getnewargs__(self):
+        return(str(self), self.token_type)
+
+
+class WhiteSpaceTerminal(Terminal):
+
+    @property
+    def value(self):
+        return ' '
+
+    def startswith_fws(self):
+        return True
+
+
+class ValueTerminal(Terminal):
+
+    @property
+    def value(self):
+        return self
+
+    def startswith_fws(self):
+        return False
+
+
+class EWWhiteSpaceTerminal(WhiteSpaceTerminal):
+
+    @property
+    def value(self):
+        return ''
+
+    def __str__(self):
+        return ''
+
+
+class _InvalidEwError(errors.HeaderParseError):
+    """Invalid encoded word found while parsing headers."""
+
+
+# XXX these need to become classes and used as instances so
+# that a program can't change them in a parse tree and screw
+# up other parse trees.  Maybe should have  tests for that, too.
+DOT = ValueTerminal('.', 'dot')
+ListSeparator = ValueTerminal(',', 'list-separator')
+RouteComponentMarker = ValueTerminal('@', 'route-component-marker')
+
+#
+# Parser
+#
+
+# Parse strings according to RFC822/2047/2822/5322 rules.
+#
+# This is a stateless parser.  Each get_XXX function accepts a string and
+# returns either a Terminal or a TokenList representing the RFC object named
+# by the method and a string containing the remaining unparsed characters
+# from the input.  Thus a parser method consumes the next syntactic construct
+# of a given type and returns a token representing the construct plus the
+# unparsed remainder of the input string.
+#
+# For example, if the first element of a structured header is a 'phrase',
+# then:
+#
+#     phrase, value = get_phrase(value)
+#
+# returns the complete phrase from the start of the string value, plus any
+# characters left in the string after the phrase is removed.
+
+_wsp_splitter = re.compile(r'([{}]+)'.format(''.join(WSP))).split
+_non_atom_end_matcher = re.compile(r"[^{}]+".format(
+    re.escape(''.join(ATOM_ENDS)))).match
+_non_printable_finder = re.compile(r"[\x00-\x20\x7F]").findall
+_non_token_end_matcher = re.compile(r"[^{}]+".format(
+    re.escape(''.join(TOKEN_ENDS)))).match
+_non_attribute_end_matcher = re.compile(r"[^{}]+".format(
+    re.escape(''.join(ATTRIBUTE_ENDS)))).match
+_non_extended_attribute_end_matcher = re.compile(r"[^{}]+".format(
+    re.escape(''.join(EXTENDED_ATTRIBUTE_ENDS)))).match
+
+def _validate_xtext(xtext):
+    """If input token contains ASCII non-printables, register a defect."""
+
+    non_printables = _non_printable_finder(xtext)
+    if non_printables:
+        xtext.defects.append(errors.NonPrintableDefect(non_printables))
+    if utils._has_surrogates(xtext):
+        xtext.defects.append(errors.UndecodableBytesDefect(
+            "Non-ASCII characters found in header token"))
+
+def _get_ptext_to_endchars(value, endchars):
+    """Scan printables/quoted-pairs until endchars and return unquoted ptext.
+
+    This function turns a run of qcontent, ccontent-without-comments, or
+    dtext-with-quoted-printables into a single string by unquoting any
+    quoted printables.  It returns the string, the remaining value, and
+    a flag that is True iff there were any quoted printables decoded.
+
+    """
+    fragment, *remainder = _wsp_splitter(value, 1)
+    vchars = []
+    escape = False
+    had_qp = False
+    for pos in range(len(fragment)):
+        if fragment[pos] == '\\':
+            if escape:
+                escape = False
+                had_qp = True
+            else:
+                escape = True
+                continue
+        if escape:
+            escape = False
+        elif fragment[pos] in endchars:
+            break
+        vchars.append(fragment[pos])
+    else:
+        pos = pos + 1
+    return ''.join(vchars), ''.join([fragment[pos:]] + remainder), had_qp
+
+def get_fws(value):
+    """FWS = 1*WSP
+
+    This isn't the RFC definition.  We're using fws to represent tokens where
+    folding can be done, but when we are parsing the *un*folding has already
+    been done so we don't need to watch out for CRLF.
+
+    """
+    newvalue = value.lstrip()
+    fws = WhiteSpaceTerminal(value[:len(value)-len(newvalue)], 'fws')
+    return fws, newvalue
+
+def get_encoded_word(value):
+    """ encoded-word = "=?" charset "?" encoding "?" encoded-text "?="
+
+    """
+    ew = EncodedWord()
+    if not value.startswith('=?'):
+        raise errors.HeaderParseError(
+            "expected encoded word but found {}".format(value))
+    tok, *remainder = value[2:].split('?=', 1)
+    if tok == value[2:]:
+        raise errors.HeaderParseError(
+            "expected encoded word but found {}".format(value))
+    remstr = ''.join(remainder)
+    if (len(remstr) > 1 and
+        remstr[0] in hexdigits and
+        remstr[1] in hexdigits and
+        tok.count('?') < 2):
+        # The ? after the CTE was followed by an encoded word escape (=XX).
+        rest, *remainder = remstr.split('?=', 1)
+        tok = tok + '?=' + rest
+    if len(tok.split()) > 1:
+        ew.defects.append(errors.InvalidHeaderDefect(
+            "whitespace inside encoded word"))
+    ew.cte = value
+    value = ''.join(remainder)
+    try:
+        text, charset, lang, defects = _ew.decode('=?' + tok + '?=')
+    except (ValueError, KeyError):
+        raise _InvalidEwError(
+            "encoded word format invalid: '{}'".format(ew.cte))
+    ew.charset = charset
+    ew.lang = lang
+    ew.defects.extend(defects)
+    while text:
+        if text[0] in WSP:
+            token, text = get_fws(text)
+            ew.append(token)
+            continue
+        chars, *remainder = _wsp_splitter(text, 1)
+        vtext = ValueTerminal(chars, 'vtext')
+        _validate_xtext(vtext)
+        ew.append(vtext)
+        text = ''.join(remainder)
+    # Encoded words should be followed by a WS
+    if value and value[0] not in WSP:
+        ew.defects.append(errors.InvalidHeaderDefect(
+            "missing trailing whitespace after encoded-word"))
+    return ew, value
+
+def get_unstructured(value):
+    """unstructured = (*([FWS] vchar) *WSP) / obs-unstruct
+       obs-unstruct = *((*LF *CR *(obs-utext) *LF *CR)) / FWS)
+       obs-utext = %d0 / obs-NO-WS-CTL / LF / CR
+
+       obs-NO-WS-CTL is control characters except WSP/CR/LF.
+
+    So, basically, we have printable runs, plus control characters or nulls in
+    the obsolete syntax, separated by whitespace.  Since RFC 2047 uses the
+    obsolete syntax in its specification, but requires whitespace on either
+    side of the encoded words, I can see no reason to need to separate the
+    non-printable-non-whitespace from the printable runs if they occur, so we
+    parse this into xtext tokens separated by WSP tokens.
+
+    Because an 'unstructured' value must by definition constitute the entire
+    value, this 'get' routine does not return a remaining value, only the
+    parsed TokenList.
+
+    """
+    # XXX: but what about bare CR and LF?  They might signal the start or
+    # end of an encoded word.  YAGNI for now, since our current parsers
+    # will never send us strings with bare CR or LF.
+
+    unstructured = UnstructuredTokenList()
+    while value:
+        if value[0] in WSP:
+            token, value = get_fws(value)
+            unstructured.append(token)
+            continue
+        valid_ew = True
+        if value.startswith('=?'):
+            try:
+                token, value = get_encoded_word(value)
+            except _InvalidEwError:
+                valid_ew = False
+            except errors.HeaderParseError:
+                # XXX: Need to figure out how to register defects when
+                # appropriate here.
+                pass
+            else:
+                have_ws = True
+                if len(unstructured) > 0:
+                    if unstructured[-1].token_type != 'fws':
+                        unstructured.defects.append(errors.InvalidHeaderDefect(
+                            "missing whitespace before encoded word"))
+                        have_ws = False
+                if have_ws and len(unstructured) > 1:
+                    if unstructured[-2].token_type == 'encoded-word':
+                        unstructured[-1] = EWWhiteSpaceTerminal(
+                            unstructured[-1], 'fws')
+                unstructured.append(token)
+                continue
+        tok, *remainder = _wsp_splitter(value, 1)
+        # Split in the middle of an atom if there is a rfc2047 encoded word
+        # which does not have WSP on both sides. The defect will be registered
+        # the next time through the loop.
+        # This needs to only be performed when the encoded word is valid;
+        # otherwise, performing it on an invalid encoded word can cause
+        # the parser to go in an infinite loop.
+        if valid_ew and rfc2047_matcher.search(tok):
+            tok, *remainder = value.partition('=?')
+        vtext = ValueTerminal(tok, 'vtext')
+        _validate_xtext(vtext)
+        unstructured.append(vtext)
+        value = ''.join(remainder)
+    return unstructured
+
+def get_qp_ctext(value):
+    r"""ctext = <printable ascii except \ ( )>
+
+    This is not the RFC ctext, since we are handling nested comments in comment
+    and unquoting quoted-pairs here.  We allow anything except the '()'
+    characters, but if we find any ASCII other than the RFC defined printable
+    ASCII, a NonPrintableDefect is added to the token's defects list.  Since
+    quoted pairs are converted to their unquoted values, what is returned is
+    a 'ptext' token.  In this case it is a WhiteSpaceTerminal, so it's value
+    is ' '.
+
+    """
+    ptext, value, _ = _get_ptext_to_endchars(value, '()')
+    ptext = WhiteSpaceTerminal(ptext, 'ptext')
+    _validate_xtext(ptext)
+    return ptext, value
+
+def get_qcontent(value):
+    """qcontent = qtext / quoted-pair
+
+    We allow anything except the DQUOTE character, but if we find any ASCII
+    other than the RFC defined printable ASCII, a NonPrintableDefect is
+    added to the token's defects list.  Any quoted pairs are converted to their
+    unquoted values, so what is returned is a 'ptext' token.  In this case it
+    is a ValueTerminal.
+
+    """
+    ptext, value, _ = _get_ptext_to_endchars(value, '"')
+    ptext = ValueTerminal(ptext, 'ptext')
+    _validate_xtext(ptext)
+    return ptext, value
+
+def get_atext(value):
+    """atext = <matches _atext_matcher>
+
+    We allow any non-ATOM_ENDS in atext, but add an InvalidATextDefect to
+    the token's defects list if we find non-atext characters.
+    """
+    m = _non_atom_end_matcher(value)
+    if not m:
+        raise errors.HeaderParseError(
+            "expected atext but found '{}'".format(value))
+    atext = m.group()
+    value = value[len(atext):]
+    atext = ValueTerminal(atext, 'atext')
+    _validate_xtext(atext)
+    return atext, value
+
+def get_bare_quoted_string(value):
+    """bare-quoted-string = DQUOTE *([FWS] qcontent) [FWS] DQUOTE
+
+    A quoted-string without the leading or trailing white space.  Its
+    value is the text between the quote marks, with whitespace
+    preserved and quoted pairs decoded.
+    """
+    if value[0] != '"':
+        raise errors.HeaderParseError(
+            "expected '\"' but found '{}'".format(value))
+    bare_quoted_string = BareQuotedString()
+    value = value[1:]
+    if value and value[0] == '"':
+        token, value = get_qcontent(value)
+        bare_quoted_string.append(token)
+    while value and value[0] != '"':
+        if value[0] in WSP:
+            token, value = get_fws(value)
+        elif value[:2] == '=?':
+            valid_ew = False
+            try:
+                token, value = get_encoded_word(value)
+                bare_quoted_string.defects.append(errors.InvalidHeaderDefect(
+                    "encoded word inside quoted string"))
+                valid_ew = True
+            except errors.HeaderParseError:
+                token, value = get_qcontent(value)
+            # Collapse the whitespace between two encoded words that occur in a
+            # bare-quoted-string.
+            if valid_ew and len(bare_quoted_string) > 1:
+                if (bare_quoted_string[-1].token_type == 'fws' and
+                        bare_quoted_string[-2].token_type == 'encoded-word'):
+                    bare_quoted_string[-1] = EWWhiteSpaceTerminal(
+                        bare_quoted_string[-1], 'fws')
+        else:
+            token, value = get_qcontent(value)
+        bare_quoted_string.append(token)
+    if not value:
+        bare_quoted_string.defects.append(errors.InvalidHeaderDefect(
+            "end of header inside quoted string"))
+        return bare_quoted_string, value
+    return bare_quoted_string, value[1:]
+
+def get_comment(value):
+    """comment = "(" *([FWS] ccontent) [FWS] ")"
+       ccontent = ctext / quoted-pair / comment
+
+    We handle nested comments here, and quoted-pair in our qp-ctext routine.
+    """
+    if value and value[0] != '(':
+        raise errors.HeaderParseError(
+            "expected '(' but found '{}'".format(value))
+    comment = Comment()
+    value = value[1:]
+    while value and value[0] != ")":
+        if value[0] in WSP:
+            token, value = get_fws(value)
+        elif value[0] == '(':
+            token, value = get_comment(value)
+        else:
+            token, value = get_qp_ctext(value)
+        comment.append(token)
+    if not value:
+        comment.defects.append(errors.InvalidHeaderDefect(
+            "end of header inside comment"))
+        return comment, value
+    return comment, value[1:]
+
+def get_cfws(value):
+    """CFWS = (1*([FWS] comment) [FWS]) / FWS
+
+    """
+    cfws = CFWSList()
+    while value and value[0] in CFWS_LEADER:
+        if value[0] in WSP:
+            token, value = get_fws(value)
+        else:
+            token, value = get_comment(value)
+        cfws.append(token)
+    return cfws, value
+
+def get_quoted_string(value):
+    """quoted-string = [CFWS] <bare-quoted-string> [CFWS]
+
+    'bare-quoted-string' is an intermediate class defined by this
+    parser and not by the RFC grammar.  It is the quoted string
+    without any attached CFWS.
+    """
+    quoted_string = QuotedString()
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        quoted_string.append(token)
+    token, value = get_bare_quoted_string(value)
+    quoted_string.append(token)
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        quoted_string.append(token)
+    return quoted_string, value
+
+def get_atom(value):
+    """atom = [CFWS] 1*atext [CFWS]
+
+    An atom could be an rfc2047 encoded word.
+    """
+    atom = Atom()
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        atom.append(token)
+    if value and value[0] in ATOM_ENDS:
+        raise errors.HeaderParseError(
+            "expected atom but found '{}'".format(value))
+    if value.startswith('=?'):
+        try:
+            token, value = get_encoded_word(value)
+        except errors.HeaderParseError:
+            # XXX: need to figure out how to register defects when
+            # appropriate here.
+            token, value = get_atext(value)
+    else:
+        token, value = get_atext(value)
+    atom.append(token)
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        atom.append(token)
+    return atom, value
+
+def get_dot_atom_text(value):
+    """ dot-text = 1*atext *("." 1*atext)
+
+    """
+    dot_atom_text = DotAtomText()
+    if not value or value[0] in ATOM_ENDS:
+        raise errors.HeaderParseError("expected atom at a start of "
+            "dot-atom-text but found '{}'".format(value))
+    while value and value[0] not in ATOM_ENDS:
+        token, value = get_atext(value)
+        dot_atom_text.append(token)
+        if value and value[0] == '.':
+            dot_atom_text.append(DOT)
+            value = value[1:]
+    if dot_atom_text[-1] is DOT:
+        raise errors.HeaderParseError("expected atom at end of dot-atom-text "
+            "but found '{}'".format('.'+value))
+    return dot_atom_text, value
+
+def get_dot_atom(value):
+    """ dot-atom = [CFWS] dot-atom-text [CFWS]
+
+    Any place we can have a dot atom, we could instead have an rfc2047 encoded
+    word.
+    """
+    dot_atom = DotAtom()
+    if value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        dot_atom.append(token)
+    if value.startswith('=?'):
+        try:
+            token, value = get_encoded_word(value)
+        except errors.HeaderParseError:
+            # XXX: need to figure out how to register defects when
+            # appropriate here.
+            token, value = get_dot_atom_text(value)
+    else:
+        token, value = get_dot_atom_text(value)
+    dot_atom.append(token)
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        dot_atom.append(token)
+    return dot_atom, value
+
+def get_word(value):
+    """word = atom / quoted-string
+
+    Either atom or quoted-string may start with CFWS.  We have to peel off this
+    CFWS first to determine which type of word to parse.  Afterward we splice
+    the leading CFWS, if any, into the parsed sub-token.
+
+    If neither an atom or a quoted-string is found before the next special, a
+    HeaderParseError is raised.
+
+    The token returned is either an Atom or a QuotedString, as appropriate.
+    This means the 'word' level of the formal grammar is not represented in the
+    parse tree; this is because having that extra layer when manipulating the
+    parse tree is more confusing than it is helpful.
+
+    """
+    if value[0] in CFWS_LEADER:
+        leader, value = get_cfws(value)
+    else:
+        leader = None
+    if not value:
+        raise errors.HeaderParseError(
+            "Expected 'atom' or 'quoted-string' but found nothing.")
+    if value[0]=='"':
+        token, value = get_quoted_string(value)
+    elif value[0] in SPECIALS:
+        raise errors.HeaderParseError("Expected 'atom' or 'quoted-string' "
+                                      "but found '{}'".format(value))
+    else:
+        token, value = get_atom(value)
+    if leader is not None:
+        token[:0] = [leader]
+    return token, value
+
+def get_phrase(value):
+    """ phrase = 1*word / obs-phrase
+        obs-phrase = word *(word / "." / CFWS)
+
+    This means a phrase can be a sequence of words, periods, and CFWS in any
+    order as long as it starts with at least one word.  If anything other than
+    words is detected, an ObsoleteHeaderDefect is added to the token's defect
+    list.  We also accept a phrase that starts with CFWS followed by a dot;
+    this is registered as an InvalidHeaderDefect, since it is not supported by
+    even the obsolete grammar.
+
+    """
+    phrase = Phrase()
+    try:
+        token, value = get_word(value)
+        phrase.append(token)
+    except errors.HeaderParseError:
+        phrase.defects.append(errors.InvalidHeaderDefect(
+            "phrase does not start with word"))
+    while value and value[0] not in PHRASE_ENDS:
+        if value[0]=='.':
+            phrase.append(DOT)
+            phrase.defects.append(errors.ObsoleteHeaderDefect(
+                "period in 'phrase'"))
+            value = value[1:]
+        else:
+            try:
+                token, value = get_word(value)
+            except errors.HeaderParseError:
+                if value[0] in CFWS_LEADER:
+                    token, value = get_cfws(value)
+                    phrase.defects.append(errors.ObsoleteHeaderDefect(
+                        "comment found without atom"))
+                else:
+                    raise
+            phrase.append(token)
+    return phrase, value
+
+def get_local_part(value):
+    """ local-part = dot-atom / quoted-string / obs-local-part
+
+    """
+    local_part = LocalPart()
+    leader = None
+    if value[0] in CFWS_LEADER:
+        leader, value = get_cfws(value)
+    if not value:
+        raise errors.HeaderParseError(
+            "expected local-part but found '{}'".format(value))
+    try:
+        token, value = get_dot_atom(value)
+    except errors.HeaderParseError:
+        try:
+            token, value = get_word(value)
+        except errors.HeaderParseError:
+            if value[0] != '\\' and value[0] in PHRASE_ENDS:
+                raise
+            token = TokenList()
+    if leader is not None:
+        token[:0] = [leader]
+    local_part.append(token)
+    if value and (value[0]=='\\' or value[0] not in PHRASE_ENDS):
+        obs_local_part, value = get_obs_local_part(str(local_part) + value)
+        if obs_local_part.token_type == 'invalid-obs-local-part':
+            local_part.defects.append(errors.InvalidHeaderDefect(
+                "local-part is not dot-atom, quoted-string, or obs-local-part"))
+        else:
+            local_part.defects.append(errors.ObsoleteHeaderDefect(
+                "local-part is not a dot-atom (contains CFWS)"))
+        local_part[0] = obs_local_part
+    try:
+        local_part.value.encode('ascii')
+    except UnicodeEncodeError:
+        local_part.defects.append(errors.NonASCIILocalPartDefect(
+                "local-part contains non-ASCII characters)"))
+    return local_part, value
+
+def get_obs_local_part(value):
+    """ obs-local-part = word *("." word)
+    """
+    obs_local_part = ObsLocalPart()
+    last_non_ws_was_dot = False
+    while value and (value[0]=='\\' or value[0] not in PHRASE_ENDS):
+        if value[0] == '.':
+            if last_non_ws_was_dot:
+                obs_local_part.defects.append(errors.InvalidHeaderDefect(
+                    "invalid repeated '.'"))
+            obs_local_part.append(DOT)
+            last_non_ws_was_dot = True
+            value = value[1:]
+            continue
+        elif value[0]=='\\':
+            obs_local_part.append(ValueTerminal(value[0],
+                                                'misplaced-special'))
+            value = value[1:]
+            obs_local_part.defects.append(errors.InvalidHeaderDefect(
+                "'\\' character outside of quoted-string/ccontent"))
+            last_non_ws_was_dot = False
+            continue
+        if obs_local_part and obs_local_part[-1].token_type != 'dot':
+            obs_local_part.defects.append(errors.InvalidHeaderDefect(
+                "missing '.' between words"))
+        try:
+            token, value = get_word(value)
+            last_non_ws_was_dot = False
+        except errors.HeaderParseError:
+            if value[0] not in CFWS_LEADER:
+                raise
+            token, value = get_cfws(value)
+        obs_local_part.append(token)
+    if (obs_local_part[0].token_type == 'dot' or
+            obs_local_part[0].token_type=='cfws' and
+            obs_local_part[1].token_type=='dot'):
+        obs_local_part.defects.append(errors.InvalidHeaderDefect(
+            "Invalid leading '.' in local part"))
+    if (obs_local_part[-1].token_type == 'dot' or
+            obs_local_part[-1].token_type=='cfws' and
+            obs_local_part[-2].token_type=='dot'):
+        obs_local_part.defects.append(errors.InvalidHeaderDefect(
+            "Invalid trailing '.' in local part"))
+    if obs_local_part.defects:
+        obs_local_part.token_type = 'invalid-obs-local-part'
+    return obs_local_part, value
+
+def get_dtext(value):
+    r""" dtext = <printable ascii except \ [ ]> / obs-dtext
+        obs-dtext = obs-NO-WS-CTL / quoted-pair
+
+    We allow anything except the excluded characters, but if we find any
+    ASCII other than the RFC defined printable ASCII, a NonPrintableDefect is
+    added to the token's defects list.  Quoted pairs are converted to their
+    unquoted values, so what is returned is a ptext token, in this case a
+    ValueTerminal.  If there were quoted-printables, an ObsoleteHeaderDefect is
+    added to the returned token's defect list.
+
+    """
+    ptext, value, had_qp = _get_ptext_to_endchars(value, '[]')
+    ptext = ValueTerminal(ptext, 'ptext')
+    if had_qp:
+        ptext.defects.append(errors.ObsoleteHeaderDefect(
+            "quoted printable found in domain-literal"))
+    _validate_xtext(ptext)
+    return ptext, value
+
+def _check_for_early_dl_end(value, domain_literal):
+    if value:
+        return False
+    domain_literal.append(errors.InvalidHeaderDefect(
+        "end of input inside domain-literal"))
+    domain_literal.append(ValueTerminal(']', 'domain-literal-end'))
+    return True
+
+def get_domain_literal(value):
+    """ domain-literal = [CFWS] "[" *([FWS] dtext) [FWS] "]" [CFWS]
+
+    """
+    domain_literal = DomainLiteral()
+    if value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        domain_literal.append(token)
+    if not value:
+        raise errors.HeaderParseError("expected domain-literal")
+    if value[0] != '[':
+        raise errors.HeaderParseError("expected '[' at start of domain-literal "
+                "but found '{}'".format(value))
+    value = value[1:]
+    if _check_for_early_dl_end(value, domain_literal):
+        return domain_literal, value
+    domain_literal.append(ValueTerminal('[', 'domain-literal-start'))
+    if value[0] in WSP:
+        token, value = get_fws(value)
+        domain_literal.append(token)
+    token, value = get_dtext(value)
+    domain_literal.append(token)
+    if _check_for_early_dl_end(value, domain_literal):
+        return domain_literal, value
+    if value[0] in WSP:
+        token, value = get_fws(value)
+        domain_literal.append(token)
+    if _check_for_early_dl_end(value, domain_literal):
+        return domain_literal, value
+    if value[0] != ']':
+        raise errors.HeaderParseError("expected ']' at end of domain-literal "
+                "but found '{}'".format(value))
+    domain_literal.append(ValueTerminal(']', 'domain-literal-end'))
+    value = value[1:]
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        domain_literal.append(token)
+    return domain_literal, value
+
+def get_domain(value):
+    """ domain = dot-atom / domain-literal / obs-domain
+        obs-domain = atom *("." atom))
+
+    """
+    domain = Domain()
+    leader = None
+    if value[0] in CFWS_LEADER:
+        leader, value = get_cfws(value)
+    if not value:
+        raise errors.HeaderParseError(
+            "expected domain but found '{}'".format(value))
+    if value[0] == '[':
+        token, value = get_domain_literal(value)
+        if leader is not None:
+            token[:0] = [leader]
+        domain.append(token)
+        return domain, value
+    try:
+        token, value = get_dot_atom(value)
+    except errors.HeaderParseError:
+        token, value = get_atom(value)
+    if value and value[0] == '@':
+        raise errors.HeaderParseError('Invalid Domain')
+    if leader is not None:
+        token[:0] = [leader]
+    domain.append(token)
+    if value and value[0] == '.':
+        domain.defects.append(errors.ObsoleteHeaderDefect(
+            "domain is not a dot-atom (contains CFWS)"))
+        if domain[0].token_type == 'dot-atom':
+            domain[:] = domain[0]
+        while value and value[0] == '.':
+            domain.append(DOT)
+            token, value = get_atom(value[1:])
+            domain.append(token)
+    return domain, value
+
+def get_addr_spec(value):
+    """ addr-spec = local-part "@" domain
+
+    """
+    addr_spec = AddrSpec()
+    token, value = get_local_part(value)
+    addr_spec.append(token)
+    if not value or value[0] != '@':
+        addr_spec.defects.append(errors.InvalidHeaderDefect(
+            "addr-spec local part with no domain"))
+        return addr_spec, value
+    addr_spec.append(ValueTerminal('@', 'address-at-symbol'))
+    token, value = get_domain(value[1:])
+    addr_spec.append(token)
+    return addr_spec, value
+
+def get_obs_route(value):
+    """ obs-route = obs-domain-list ":"
+        obs-domain-list = *(CFWS / ",") "@" domain *("," [CFWS] ["@" domain])
+
+        Returns an obs-route token with the appropriate sub-tokens (that is,
+        there is no obs-domain-list in the parse tree).
+    """
+    obs_route = ObsRoute()
+    while value and (value[0]==',' or value[0] in CFWS_LEADER):
+        if value[0] in CFWS_LEADER:
+            token, value = get_cfws(value)
+            obs_route.append(token)
+        elif value[0] == ',':
+            obs_route.append(ListSeparator)
+            value = value[1:]
+    if not value or value[0] != '@':
+        raise errors.HeaderParseError(
+            "expected obs-route domain but found '{}'".format(value))
+    obs_route.append(RouteComponentMarker)
+    token, value = get_domain(value[1:])
+    obs_route.append(token)
+    while value and value[0]==',':
+        obs_route.append(ListSeparator)
+        value = value[1:]
+        if not value:
+            break
+        if value[0] in CFWS_LEADER:
+            token, value = get_cfws(value)
+            obs_route.append(token)
+        if value[0] == '@':
+            obs_route.append(RouteComponentMarker)
+            token, value = get_domain(value[1:])
+            obs_route.append(token)
+    if not value:
+        raise errors.HeaderParseError("end of header while parsing obs-route")
+    if value[0] != ':':
+        raise errors.HeaderParseError( "expected ':' marking end of "
+            "obs-route but found '{}'".format(value))
+    obs_route.append(ValueTerminal(':', 'end-of-obs-route-marker'))
+    return obs_route, value[1:]
+
+def get_angle_addr(value):
+    """ angle-addr = [CFWS] "<" addr-spec ">" [CFWS] / obs-angle-addr
+        obs-angle-addr = [CFWS] "<" obs-route addr-spec ">" [CFWS]
+
+    """
+    angle_addr = AngleAddr()
+    if value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        angle_addr.append(token)
+    if not value or value[0] != '<':
+        raise errors.HeaderParseError(
+            "expected angle-addr but found '{}'".format(value))
+    angle_addr.append(ValueTerminal('<', 'angle-addr-start'))
+    value = value[1:]
+    # Although it is not legal per RFC5322, SMTP uses '<>' in certain
+    # circumstances.
+    if value[0] == '>':
+        angle_addr.append(ValueTerminal('>', 'angle-addr-end'))
+        angle_addr.defects.append(errors.InvalidHeaderDefect(
+            "null addr-spec in angle-addr"))
+        value = value[1:]
+        return angle_addr, value
+    try:
+        token, value = get_addr_spec(value)
+    except errors.HeaderParseError:
+        try:
+            token, value = get_obs_route(value)
+            angle_addr.defects.append(errors.ObsoleteHeaderDefect(
+                "obsolete route specification in angle-addr"))
+        except errors.HeaderParseError:
+            raise errors.HeaderParseError(
+                "expected addr-spec or obs-route but found '{}'".format(value))
+        angle_addr.append(token)
+        token, value = get_addr_spec(value)
+    angle_addr.append(token)
+    if value and value[0] == '>':
+        value = value[1:]
+    else:
+        angle_addr.defects.append(errors.InvalidHeaderDefect(
+            "missing trailing '>' on angle-addr"))
+    angle_addr.append(ValueTerminal('>', 'angle-addr-end'))
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        angle_addr.append(token)
+    return angle_addr, value
+
+def get_display_name(value):
+    """ display-name = phrase
+
+    Because this is simply a name-rule, we don't return a display-name
+    token containing a phrase, but rather a display-name token with
+    the content of the phrase.
+
+    """
+    display_name = DisplayName()
+    token, value = get_phrase(value)
+    display_name.extend(token[:])
+    display_name.defects = token.defects[:]
+    return display_name, value
+
+
+def get_name_addr(value):
+    """ name-addr = [display-name] angle-addr
+
+    """
+    name_addr = NameAddr()
+    # Both the optional display name and the angle-addr can start with cfws.
+    leader = None
+    if value[0] in CFWS_LEADER:
+        leader, value = get_cfws(value)
+        if not value:
+            raise errors.HeaderParseError(
+                "expected name-addr but found '{}'".format(leader))
+    if value[0] != '<':
+        if value[0] in PHRASE_ENDS:
+            raise errors.HeaderParseError(
+                "expected name-addr but found '{}'".format(value))
+        token, value = get_display_name(value)
+        if not value:
+            raise errors.HeaderParseError(
+                "expected name-addr but found '{}'".format(token))
+        if leader is not None:
+            token[0][:0] = [leader]
+            leader = None
+        name_addr.append(token)
+    token, value = get_angle_addr(value)
+    if leader is not None:
+        token[:0] = [leader]
+    name_addr.append(token)
+    return name_addr, value
+
+def get_mailbox(value):
+    """ mailbox = name-addr / addr-spec
+
+    """
+    # The only way to figure out if we are dealing with a name-addr or an
+    # addr-spec is to try parsing each one.
+    mailbox = Mailbox()
+    try:
+        token, value = get_name_addr(value)
+    except errors.HeaderParseError:
+        try:
+            token, value = get_addr_spec(value)
+        except errors.HeaderParseError:
+            raise errors.HeaderParseError(
+                "expected mailbox but found '{}'".format(value))
+    if any(isinstance(x, errors.InvalidHeaderDefect)
+                       for x in token.all_defects):
+        mailbox.token_type = 'invalid-mailbox'
+    mailbox.append(token)
+    return mailbox, value
+
+def get_invalid_mailbox(value, endchars):
+    """ Read everything up to one of the chars in endchars.
+
+    This is outside the formal grammar.  The InvalidMailbox TokenList that is
+    returned acts like a Mailbox, but the data attributes are None.
+
+    """
+    invalid_mailbox = InvalidMailbox()
+    while value and value[0] not in endchars:
+        if value[0] in PHRASE_ENDS:
+            invalid_mailbox.append(ValueTerminal(value[0],
+                                                 'misplaced-special'))
+            value = value[1:]
+        else:
+            token, value = get_phrase(value)
+            invalid_mailbox.append(token)
+    return invalid_mailbox, value
+
+def get_mailbox_list(value):
+    """ mailbox-list = (mailbox *("," mailbox)) / obs-mbox-list
+        obs-mbox-list = *([CFWS] ",") mailbox *("," [mailbox / CFWS])
+
+    For this routine we go outside the formal grammar in order to improve error
+    handling.  We recognize the end of the mailbox list only at the end of the
+    value or at a ';' (the group terminator).  This is so that we can turn
+    invalid mailboxes into InvalidMailbox tokens and continue parsing any
+    remaining valid mailboxes.  We also allow all mailbox entries to be null,
+    and this condition is handled appropriately at a higher level.
+
+    """
+    mailbox_list = MailboxList()
+    while value and value[0] != ';':
+        try:
+            token, value = get_mailbox(value)
+            mailbox_list.append(token)
+        except errors.HeaderParseError:
+            leader = None
+            if value[0] in CFWS_LEADER:
+                leader, value = get_cfws(value)
+                if not value or value[0] in ',;':
+                    mailbox_list.append(leader)
+                    mailbox_list.defects.append(errors.ObsoleteHeaderDefect(
+                        "empty element in mailbox-list"))
+                else:
+                    token, value = get_invalid_mailbox(value, ',;')
+                    if leader is not None:
+                        token[:0] = [leader]
+                    mailbox_list.append(token)
+                    mailbox_list.defects.append(errors.InvalidHeaderDefect(
+                        "invalid mailbox in mailbox-list"))
+            elif value[0] == ',':
+                mailbox_list.defects.append(errors.ObsoleteHeaderDefect(
+                    "empty element in mailbox-list"))
+            else:
+                token, value = get_invalid_mailbox(value, ',;')
+                if leader is not None:
+                    token[:0] = [leader]
+                mailbox_list.append(token)
+                mailbox_list.defects.append(errors.InvalidHeaderDefect(
+                    "invalid mailbox in mailbox-list"))
+        if value and value[0] not in ',;':
+            # Crap after mailbox; treat it as an invalid mailbox.
+            # The mailbox info will still be available.
+            mailbox = mailbox_list[-1]
+            mailbox.token_type = 'invalid-mailbox'
+            token, value = get_invalid_mailbox(value, ',;')
+            mailbox.extend(token)
+            mailbox_list.defects.append(errors.InvalidHeaderDefect(
+                "invalid mailbox in mailbox-list"))
+        if value and value[0] == ',':
+            mailbox_list.append(ListSeparator)
+            value = value[1:]
+    return mailbox_list, value
+
+
+def get_group_list(value):
+    """ group-list = mailbox-list / CFWS / obs-group-list
+        obs-group-list = 1*([CFWS] ",") [CFWS]
+
+    """
+    group_list = GroupList()
+    if not value:
+        group_list.defects.append(errors.InvalidHeaderDefect(
+            "end of header before group-list"))
+        return group_list, value
+    leader = None
+    if value and value[0] in CFWS_LEADER:
+        leader, value = get_cfws(value)
+        if not value:
+            # This should never happen in email parsing, since CFWS-only is a
+            # legal alternative to group-list in a group, which is the only
+            # place group-list appears.
+            group_list.defects.append(errors.InvalidHeaderDefect(
+                "end of header in group-list"))
+            group_list.append(leader)
+            return group_list, value
+        if value[0] == ';':
+            group_list.append(leader)
+            return group_list, value
+    token, value = get_mailbox_list(value)
+    if len(token.all_mailboxes)==0:
+        if leader is not None:
+            group_list.append(leader)
+        group_list.extend(token)
+        group_list.defects.append(errors.ObsoleteHeaderDefect(
+            "group-list with empty entries"))
+        return group_list, value
+    if leader is not None:
+        token[:0] = [leader]
+    group_list.append(token)
+    return group_list, value
+
+def get_group(value):
+    """ group = display-name ":" [group-list] ";" [CFWS]
+
+    """
+    group = Group()
+    token, value = get_display_name(value)
+    if not value or value[0] != ':':
+        raise errors.HeaderParseError("expected ':' at end of group "
+            "display name but found '{}'".format(value))
+    group.append(token)
+    group.append(ValueTerminal(':', 'group-display-name-terminator'))
+    value = value[1:]
+    if value and value[0] == ';':
+        group.append(ValueTerminal(';', 'group-terminator'))
+        return group, value[1:]
+    token, value = get_group_list(value)
+    group.append(token)
+    if not value:
+        group.defects.append(errors.InvalidHeaderDefect(
+            "end of header in group"))
+    elif value[0] != ';':
+        raise errors.HeaderParseError(
+            "expected ';' at end of group but found {}".format(value))
+    group.append(ValueTerminal(';', 'group-terminator'))
+    value = value[1:]
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        group.append(token)
+    return group, value
+
+def get_address(value):
+    """ address = mailbox / group
+
+    Note that counter-intuitively, an address can be either a single address or
+    a list of addresses (a group).  This is why the returned Address object has
+    a 'mailboxes' attribute which treats a single address as a list of length
+    one.  When you need to differentiate between to two cases, extract the single
+    element, which is either a mailbox or a group token.
+
+    """
+    # The formal grammar isn't very helpful when parsing an address.  mailbox
+    # and group, especially when allowing for obsolete forms, start off very
+    # similarly.  It is only when you reach one of @, <, or : that you know
+    # what you've got.  So, we try each one in turn, starting with the more
+    # likely of the two.  We could perhaps make this more efficient by looking
+    # for a phrase and then branching based on the next character, but that
+    # would be a premature optimization.
+    address = Address()
+    try:
+        token, value = get_group(value)
+    except errors.HeaderParseError:
+        try:
+            token, value = get_mailbox(value)
+        except errors.HeaderParseError:
+            raise errors.HeaderParseError(
+                "expected address but found '{}'".format(value))
+    address.append(token)
+    return address, value
+
+def get_address_list(value):
+    """ address_list = (address *("," address)) / obs-addr-list
+        obs-addr-list = *([CFWS] ",") address *("," [address / CFWS])
+
+    We depart from the formal grammar here by continuing to parse until the end
+    of the input, assuming the input to be entirely composed of an
+    address-list.  This is always true in email parsing, and allows us
+    to skip invalid addresses to parse additional valid ones.
+
+    """
+    address_list = AddressList()
+    while value:
+        try:
+            token, value = get_address(value)
+            address_list.append(token)
+        except errors.HeaderParseError as err:
+            leader = None
+            if value[0] in CFWS_LEADER:
+                leader, value = get_cfws(value)
+                if not value or value[0] == ',':
+                    address_list.append(leader)
+                    address_list.defects.append(errors.ObsoleteHeaderDefect(
+                        "address-list entry with no content"))
+                else:
+                    token, value = get_invalid_mailbox(value, ',')
+                    if leader is not None:
+                        token[:0] = [leader]
+                    address_list.append(Address([token]))
+                    address_list.defects.append(errors.InvalidHeaderDefect(
+                        "invalid address in address-list"))
+            elif value[0] == ',':
+                address_list.defects.append(errors.ObsoleteHeaderDefect(
+                    "empty element in address-list"))
+            else:
+                token, value = get_invalid_mailbox(value, ',')
+                if leader is not None:
+                    token[:0] = [leader]
+                address_list.append(Address([token]))
+                address_list.defects.append(errors.InvalidHeaderDefect(
+                    "invalid address in address-list"))
+        if value and value[0] != ',':
+            # Crap after address; treat it as an invalid mailbox.
+            # The mailbox info will still be available.
+            mailbox = address_list[-1][0]
+            mailbox.token_type = 'invalid-mailbox'
+            token, value = get_invalid_mailbox(value, ',')
+            mailbox.extend(token)
+            address_list.defects.append(errors.InvalidHeaderDefect(
+                "invalid address in address-list"))
+        if value:  # Must be a , at this point.
+            address_list.append(ValueTerminal(',', 'list-separator'))
+            value = value[1:]
+    return address_list, value
+
+
+def get_no_fold_literal(value):
+    """ no-fold-literal = "[" *dtext "]"
+    """
+    no_fold_literal = NoFoldLiteral()
+    if not value:
+        raise errors.HeaderParseError(
+            "expected no-fold-literal but found '{}'".format(value))
+    if value[0] != '[':
+        raise errors.HeaderParseError(
+            "expected '[' at the start of no-fold-literal "
+            "but found '{}'".format(value))
+    no_fold_literal.append(ValueTerminal('[', 'no-fold-literal-start'))
+    value = value[1:]
+    token, value = get_dtext(value)
+    no_fold_literal.append(token)
+    if not value or value[0] != ']':
+        raise errors.HeaderParseError(
+            "expected ']' at the end of no-fold-literal "
+            "but found '{}'".format(value))
+    no_fold_literal.append(ValueTerminal(']', 'no-fold-literal-end'))
+    return no_fold_literal, value[1:]
+
+def get_msg_id(value):
+    """msg-id = [CFWS] "<" id-left '@' id-right  ">" [CFWS]
+       id-left = dot-atom-text / obs-id-left
+       id-right = dot-atom-text / no-fold-literal / obs-id-right
+       no-fold-literal = "[" *dtext "]"
+    """
+    msg_id = MsgID()
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        msg_id.append(token)
+    if not value or value[0] != '<':
+        raise errors.HeaderParseError(
+            "expected msg-id but found '{}'".format(value))
+    msg_id.append(ValueTerminal('<', 'msg-id-start'))
+    value = value[1:]
+    # Parse id-left.
+    try:
+        token, value = get_dot_atom_text(value)
+    except errors.HeaderParseError:
+        try:
+            # obs-id-left is same as local-part of add-spec.
+            token, value = get_obs_local_part(value)
+            msg_id.defects.append(errors.ObsoleteHeaderDefect(
+                "obsolete id-left in msg-id"))
+        except errors.HeaderParseError:
+            raise errors.HeaderParseError(
+                "expected dot-atom-text or obs-id-left"
+                " but found '{}'".format(value))
+    msg_id.append(token)
+    if not value or value[0] != '@':
+        msg_id.defects.append(errors.InvalidHeaderDefect(
+            "msg-id with no id-right"))
+        # Even though there is no id-right, if the local part
+        # ends with `>` let's just parse it too and return
+        # along with the defect.
+        if value and value[0] == '>':
+            msg_id.append(ValueTerminal('>', 'msg-id-end'))
+            value = value[1:]
+        return msg_id, value
+    msg_id.append(ValueTerminal('@', 'address-at-symbol'))
+    value = value[1:]
+    # Parse id-right.
+    try:
+        token, value = get_dot_atom_text(value)
+    except errors.HeaderParseError:
+        try:
+            token, value = get_no_fold_literal(value)
+        except errors.HeaderParseError as e:
+            try:
+                token, value = get_domain(value)
+                msg_id.defects.append(errors.ObsoleteHeaderDefect(
+                    "obsolete id-right in msg-id"))
+            except errors.HeaderParseError:
+                raise errors.HeaderParseError(
+                    "expected dot-atom-text, no-fold-literal or obs-id-right"
+                    " but found '{}'".format(value))
+    msg_id.append(token)
+    if value and value[0] == '>':
+        value = value[1:]
+    else:
+        msg_id.defects.append(errors.InvalidHeaderDefect(
+            "missing trailing '>' on msg-id"))
+    msg_id.append(ValueTerminal('>', 'msg-id-end'))
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        msg_id.append(token)
+    return msg_id, value
+
+
+def parse_message_id(value):
+    """message-id      =   "Message-ID:" msg-id CRLF
+    """
+    message_id = MessageID()
+    try:
+        token, value = get_msg_id(value)
+        message_id.append(token)
+    except errors.HeaderParseError as ex:
+        token = get_unstructured(value)
+        message_id = InvalidMessageID(token)
+        message_id.defects.append(
+            errors.InvalidHeaderDefect("Invalid msg-id: {!r}".format(ex)))
+    else:
+        # Value after parsing a valid msg_id should be None.
+        if value:
+            message_id.defects.append(errors.InvalidHeaderDefect(
+                "Unexpected {!r}".format(value)))
+
+    return message_id
+
+#
+# XXX: As I begin to add additional header parsers, I'm realizing we probably
+# have two level of parser routines: the get_XXX methods that get a token in
+# the grammar, and parse_XXX methods that parse an entire field value.  So
+# get_address_list above should really be a parse_ method, as probably should
+# be get_unstructured.
+#
+
+def parse_mime_version(value):
+    """ mime-version = [CFWS] 1*digit [CFWS] "." [CFWS] 1*digit [CFWS]
+
+    """
+    # The [CFWS] is implicit in the RFC 2045 BNF.
+    # XXX: This routine is a bit verbose, should factor out a get_int method.
+    mime_version = MIMEVersion()
+    if not value:
+        mime_version.defects.append(errors.HeaderMissingRequiredValue(
+            "Missing MIME version number (eg: 1.0)"))
+        return mime_version
+    if value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        mime_version.append(token)
+        if not value:
+            mime_version.defects.append(errors.HeaderMissingRequiredValue(
+                "Expected MIME version number but found only CFWS"))
+    digits = ''
+    while value and value[0] != '.' and value[0] not in CFWS_LEADER:
+        digits += value[0]
+        value = value[1:]
+    if not digits.isdigit():
+        mime_version.defects.append(errors.InvalidHeaderDefect(
+            "Expected MIME major version number but found {!r}".format(digits)))
+        mime_version.append(ValueTerminal(digits, 'xtext'))
+    else:
+        mime_version.major = int(digits)
+        mime_version.append(ValueTerminal(digits, 'digits'))
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        mime_version.append(token)
+    if not value or value[0] != '.':
+        if mime_version.major is not None:
+            mime_version.defects.append(errors.InvalidHeaderDefect(
+                "Incomplete MIME version; found only major number"))
+        if value:
+            mime_version.append(ValueTerminal(value, 'xtext'))
+        return mime_version
+    mime_version.append(ValueTerminal('.', 'version-separator'))
+    value = value[1:]
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        mime_version.append(token)
+    if not value:
+        if mime_version.major is not None:
+            mime_version.defects.append(errors.InvalidHeaderDefect(
+                "Incomplete MIME version; found only major number"))
+        return mime_version
+    digits = ''
+    while value and value[0] not in CFWS_LEADER:
+        digits += value[0]
+        value = value[1:]
+    if not digits.isdigit():
+        mime_version.defects.append(errors.InvalidHeaderDefect(
+            "Expected MIME minor version number but found {!r}".format(digits)))
+        mime_version.append(ValueTerminal(digits, 'xtext'))
+    else:
+        mime_version.minor = int(digits)
+        mime_version.append(ValueTerminal(digits, 'digits'))
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        mime_version.append(token)
+    if value:
+        mime_version.defects.append(errors.InvalidHeaderDefect(
+            "Excess non-CFWS text after MIME version"))
+        mime_version.append(ValueTerminal(value, 'xtext'))
+    return mime_version
+
+def get_invalid_parameter(value):
+    """ Read everything up to the next ';'.
+
+    This is outside the formal grammar.  The InvalidParameter TokenList that is
+    returned acts like a Parameter, but the data attributes are None.
+
+    """
+    invalid_parameter = InvalidParameter()
+    while value and value[0] != ';':
+        if value[0] in PHRASE_ENDS:
+            invalid_parameter.append(ValueTerminal(value[0],
+                                                   'misplaced-special'))
+            value = value[1:]
+        else:
+            token, value = get_phrase(value)
+            invalid_parameter.append(token)
+    return invalid_parameter, value
+
+def get_ttext(value):
+    """ttext = <matches _ttext_matcher>
+
+    We allow any non-TOKEN_ENDS in ttext, but add defects to the token's
+    defects list if we find non-ttext characters.  We also register defects for
+    *any* non-printables even though the RFC doesn't exclude all of them,
+    because we follow the spirit of RFC 5322.
+
+    """
+    m = _non_token_end_matcher(value)
+    if not m:
+        raise errors.HeaderParseError(
+            "expected ttext but found '{}'".format(value))
+    ttext = m.group()
+    value = value[len(ttext):]
+    ttext = ValueTerminal(ttext, 'ttext')
+    _validate_xtext(ttext)
+    return ttext, value
+
+def get_token(value):
+    """token = [CFWS] 1*ttext [CFWS]
+
+    The RFC equivalent of ttext is any US-ASCII chars except space, ctls, or
+    tspecials.  We also exclude tabs even though the RFC doesn't.
+
+    The RFC implies the CFWS but is not explicit about it in the BNF.
+
+    """
+    mtoken = Token()
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        mtoken.append(token)
+    if value and value[0] in TOKEN_ENDS:
+        raise errors.HeaderParseError(
+            "expected token but found '{}'".format(value))
+    token, value = get_ttext(value)
+    mtoken.append(token)
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        mtoken.append(token)
+    return mtoken, value
+
+def get_attrtext(value):
+    """attrtext = 1*(any non-ATTRIBUTE_ENDS character)
+
+    We allow any non-ATTRIBUTE_ENDS in attrtext, but add defects to the
+    token's defects list if we find non-attrtext characters.  We also register
+    defects for *any* non-printables even though the RFC doesn't exclude all of
+    them, because we follow the spirit of RFC 5322.
+
+    """
+    m = _non_attribute_end_matcher(value)
+    if not m:
+        raise errors.HeaderParseError(
+            "expected attrtext but found {!r}".format(value))
+    attrtext = m.group()
+    value = value[len(attrtext):]
+    attrtext = ValueTerminal(attrtext, 'attrtext')
+    _validate_xtext(attrtext)
+    return attrtext, value
+
+def get_attribute(value):
+    """ [CFWS] 1*attrtext [CFWS]
+
+    This version of the BNF makes the CFWS explicit, and as usual we use a
+    value terminal for the actual run of characters.  The RFC equivalent of
+    attrtext is the token characters, with the subtraction of '*', "'", and '%'.
+    We include tab in the excluded set just as we do for token.
+
+    """
+    attribute = Attribute()
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        attribute.append(token)
+    if value and value[0] in ATTRIBUTE_ENDS:
+        raise errors.HeaderParseError(
+            "expected token but found '{}'".format(value))
+    token, value = get_attrtext(value)
+    attribute.append(token)
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        attribute.append(token)
+    return attribute, value
+
+def get_extended_attrtext(value):
+    """attrtext = 1*(any non-ATTRIBUTE_ENDS character plus '%')
+
+    This is a special parsing routine so that we get a value that
+    includes % escapes as a single string (which we decode as a single
+    string later).
+
+    """
+    m = _non_extended_attribute_end_matcher(value)
+    if not m:
+        raise errors.HeaderParseError(
+            "expected extended attrtext but found {!r}".format(value))
+    attrtext = m.group()
+    value = value[len(attrtext):]
+    attrtext = ValueTerminal(attrtext, 'extended-attrtext')
+    _validate_xtext(attrtext)
+    return attrtext, value
+
+def get_extended_attribute(value):
+    """ [CFWS] 1*extended_attrtext [CFWS]
+
+    This is like the non-extended version except we allow % characters, so that
+    we can pick up an encoded value as a single string.
+
+    """
+    # XXX: should we have an ExtendedAttribute TokenList?
+    attribute = Attribute()
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        attribute.append(token)
+    if value and value[0] in EXTENDED_ATTRIBUTE_ENDS:
+        raise errors.HeaderParseError(
+            "expected token but found '{}'".format(value))
+    token, value = get_extended_attrtext(value)
+    attribute.append(token)
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        attribute.append(token)
+    return attribute, value
+
+def get_section(value):
+    """ '*' digits
+
+    The formal BNF is more complicated because leading 0s are not allowed.  We
+    check for that and add a defect.  We also assume no CFWS is allowed between
+    the '*' and the digits, though the RFC is not crystal clear on that.
+    The caller should already have dealt with leading CFWS.
+
+    """
+    section = Section()
+    if not value or value[0] != '*':
+        raise errors.HeaderParseError("Expected section but found {}".format(
+                                        value))
+    section.append(ValueTerminal('*', 'section-marker'))
+    value = value[1:]
+    if not value or not value[0].isdigit():
+        raise errors.HeaderParseError("Expected section number but "
+                                      "found {}".format(value))
+    digits = ''
+    while value and value[0].isdigit():
+        digits += value[0]
+        value = value[1:]
+    if digits[0] == '0' and digits != '0':
+        section.defects.append(errors.InvalidHeaderError(
+                "section number has an invalid leading 0"))
+    section.number = int(digits)
+    section.append(ValueTerminal(digits, 'digits'))
+    return section, value
+
+
+def get_value(value):
+    """ quoted-string / attribute
+
+    """
+    v = Value()
+    if not value:
+        raise errors.HeaderParseError("Expected value but found end of string")
+    leader = None
+    if value[0] in CFWS_LEADER:
+        leader, value = get_cfws(value)
+    if not value:
+        raise errors.HeaderParseError("Expected value but found "
+                                      "only {}".format(leader))
+    if value[0] == '"':
+        token, value = get_quoted_string(value)
+    else:
+        token, value = get_extended_attribute(value)
+    if leader is not None:
+        token[:0] = [leader]
+    v.append(token)
+    return v, value
+
+def get_parameter(value):
+    """ attribute [section] ["*"] [CFWS] "=" value
+
+    The CFWS is implied by the RFC but not made explicit in the BNF.  This
+    simplified form of the BNF from the RFC is made to conform with the RFC BNF
+    through some extra checks.  We do it this way because it makes both error
+    recovery and working with the resulting parse tree easier.
+    """
+    # It is possible CFWS would also be implicitly allowed between the section
+    # and the 'extended-attribute' marker (the '*') , but we've never seen that
+    # in the wild and we will therefore ignore the possibility.
+    param = Parameter()
+    token, value = get_attribute(value)
+    param.append(token)
+    if not value or value[0] == ';':
+        param.defects.append(errors.InvalidHeaderDefect("Parameter contains "
+            "name ({}) but no value".format(token)))
+        return param, value
+    if value[0] == '*':
+        try:
+            token, value = get_section(value)
+            param.sectioned = True
+            param.append(token)
+        except errors.HeaderParseError:
+            pass
+        if not value:
+            raise errors.HeaderParseError("Incomplete parameter")
+        if value[0] == '*':
+            param.append(ValueTerminal('*', 'extended-parameter-marker'))
+            value = value[1:]
+            param.extended = True
+    if value[0] != '=':
+        raise errors.HeaderParseError("Parameter not followed by '='")
+    param.append(ValueTerminal('=', 'parameter-separator'))
+    value = value[1:]
+    leader = None
+    if value and value[0] in CFWS_LEADER:
+        token, value = get_cfws(value)
+        param.append(token)
+    remainder = None
+    appendto = param
+    if param.extended and value and value[0] == '"':
+        # Now for some serious hackery to handle the common invalid case of
+        # double quotes around an extended value.  We also accept (with defect)
+        # a value marked as encoded that isn't really.
+        qstring, remainder = get_quoted_string(value)
+        inner_value = qstring.stripped_value
+        semi_valid = False
+        if param.section_number == 0:
+            if inner_value and inner_value[0] == "'":
+                semi_valid = True
+            else:
+                token, rest = get_attrtext(inner_value)
+                if rest and rest[0] == "'":
+                    semi_valid = True
+        else:
+            try:
+                token, rest = get_extended_attrtext(inner_value)
+            except:
+                pass
+            else:
+                if not rest:
+                    semi_valid = True
+        if semi_valid:
+            param.defects.append(errors.InvalidHeaderDefect(
+                "Quoted string value for extended parameter is invalid"))
+            param.append(qstring)
+            for t in qstring:
+                if t.token_type == 'bare-quoted-string':
+                    t[:] = []
+                    appendto = t
+                    break
+            value = inner_value
+        else:
+            remainder = None
+            param.defects.append(errors.InvalidHeaderDefect(
+                "Parameter marked as extended but appears to have a "
+                "quoted string value that is non-encoded"))
+    if value and value[0] == "'":
+        token = None
+    else:
+        token, value = get_value(value)
+    if not param.extended or param.section_number > 0:
+        if not value or value[0] != "'":
+            appendto.append(token)
+            if remainder is not None:
+                assert not value, value
+                value = remainder
+            return param, value
+        param.defects.append(errors.InvalidHeaderDefect(
+            "Apparent initial-extended-value but attribute "
+            "was not marked as extended or was not initial section"))
+    if not value:
+        # Assume the charset/lang is missing and the token is the value.
+        param.defects.append(errors.InvalidHeaderDefect(
+            "Missing required charset/lang delimiters"))
+        appendto.append(token)
+        if remainder is None:
+            return param, value
+    else:
+        if token is not None:
+            for t in token:
+                if t.token_type == 'extended-attrtext':
+                    break
+            t.token_type == 'attrtext'
+            appendto.append(t)
+            param.charset = t.value
+        if value[0] != "'":
+            raise errors.HeaderParseError("Expected RFC2231 char/lang encoding "
+                                          "delimiter, but found {!r}".format(value))
+        appendto.append(ValueTerminal("'", 'RFC2231-delimiter'))
+        value = value[1:]
+        if value and value[0] != "'":
+            token, value = get_attrtext(value)
+            appendto.append(token)
+            param.lang = token.value
+            if not value or value[0] != "'":
+                raise errors.HeaderParseError("Expected RFC2231 char/lang encoding "
+                                  "delimiter, but found {}".format(value))
+        appendto.append(ValueTerminal("'", 'RFC2231-delimiter'))
+        value = value[1:]
+    if remainder is not None:
+        # Treat the rest of value as bare quoted string content.
+        v = Value()
+        while value:
+            if value[0] in WSP:
+                token, value = get_fws(value)
+            elif value[0] == '"':
+                token = ValueTerminal('"', 'DQUOTE')
+                value = value[1:]
+            else:
+                token, value = get_qcontent(value)
+            v.append(token)
+        token = v
+    else:
+        token, value = get_value(value)
+    appendto.append(token)
+    if remainder is not None:
+        assert not value, value
+        value = remainder
+    return param, value
+
+def parse_mime_parameters(value):
+    """ parameter *( ";" parameter )
+
+    That BNF is meant to indicate this routine should only be called after
+    finding and handling the leading ';'.  There is no corresponding rule in
+    the formal RFC grammar, but it is more convenient for us for the set of
+    parameters to be treated as its own TokenList.
+
+    This is 'parse' routine because it consumes the remaining value, but it
+    would never be called to parse a full header.  Instead it is called to
+    parse everything after the non-parameter value of a specific MIME header.
+
+    """
+    mime_parameters = MimeParameters()
+    while value:
+        try:
+            token, value = get_parameter(value)
+            mime_parameters.append(token)
+        except errors.HeaderParseError as err:
+            leader = None
+            if value[0] in CFWS_LEADER:
+                leader, value = get_cfws(value)
+            if not value:
+                mime_parameters.append(leader)
+                return mime_parameters
+            if value[0] == ';':
+                if leader is not None:
+                    mime_parameters.append(leader)
+                mime_parameters.defects.append(errors.InvalidHeaderDefect(
+                    "parameter entry with no content"))
+            else:
+                token, value = get_invalid_parameter(value)
+                if leader:
+                    token[:0] = [leader]
+                mime_parameters.append(token)
+                mime_parameters.defects.append(errors.InvalidHeaderDefect(
+                    "invalid parameter {!r}".format(token)))
+        if value and value[0] != ';':
+            # Junk after the otherwise valid parameter.  Mark it as
+            # invalid, but it will have a value.
+            param = mime_parameters[-1]
+            param.token_type = 'invalid-parameter'
+            token, value = get_invalid_parameter(value)
+            param.extend(token)
+            mime_parameters.defects.append(errors.InvalidHeaderDefect(
+                "parameter with invalid trailing text {!r}".format(token)))
+        if value:
+            # Must be a ';' at this point.
+            mime_parameters.append(ValueTerminal(';', 'parameter-separator'))
+            value = value[1:]
+    return mime_parameters
+
+def _find_mime_parameters(tokenlist, value):
+    """Do our best to find the parameters in an invalid MIME header
+
+    """
+    while value and value[0] != ';':
+        if value[0] in PHRASE_ENDS:
+            tokenlist.append(ValueTerminal(value[0], 'misplaced-special'))
+            value = value[1:]
+        else:
+            token, value = get_phrase(value)
+            tokenlist.append(token)
+    if not value:
+        return
+    tokenlist.append(ValueTerminal(';', 'parameter-separator'))
+    tokenlist.append(parse_mime_parameters(value[1:]))
+
+def parse_content_type_header(value):
+    """ maintype "/" subtype *( ";" parameter )
+
+    The maintype and substype are tokens.  Theoretically they could
+    be checked against the official IANA list + x-token, but we
+    don't do that.
+    """
+    ctype = ContentType()
+    recover = False
+    if not value:
+        ctype.defects.append(errors.HeaderMissingRequiredValue(
+            "Missing content type specification"))
+        return ctype
+    try:
+        token, value = get_token(value)
+    except errors.HeaderParseError:
+        ctype.defects.append(errors.InvalidHeaderDefect(
+            "Expected content maintype but found {!r}".format(value)))
+        _find_mime_parameters(ctype, value)
+        return ctype
+    ctype.append(token)
+    # XXX: If we really want to follow the formal grammar we should make
+    # mantype and subtype specialized TokenLists here.  Probably not worth it.
+    if not value or value[0] != '/':
+        ctype.defects.append(errors.InvalidHeaderDefect(
+            "Invalid content type"))
+        if value:
+            _find_mime_parameters(ctype, value)
+        return ctype
+    ctype.maintype = token.value.strip().lower()
+    ctype.append(ValueTerminal('/', 'content-type-separator'))
+    value = value[1:]
+    try:
+        token, value = get_token(value)
+    except errors.HeaderParseError:
+        ctype.defects.append(errors.InvalidHeaderDefect(
+            "Expected content subtype but found {!r}".format(value)))
+        _find_mime_parameters(ctype, value)
+        return ctype
+    ctype.append(token)
+    ctype.subtype = token.value.strip().lower()
+    if not value:
+        return ctype
+    if value[0] != ';':
+        ctype.defects.append(errors.InvalidHeaderDefect(
+            "Only parameters are valid after content type, but "
+            "found {!r}".format(value)))
+        # The RFC requires that a syntactically invalid content-type be treated
+        # as text/plain.  Perhaps we should postel this, but we should probably
+        # only do that if we were checking the subtype value against IANA.
+        del ctype.maintype, ctype.subtype
+        _find_mime_parameters(ctype, value)
+        return ctype
+    ctype.append(ValueTerminal(';', 'parameter-separator'))
+    ctype.append(parse_mime_parameters(value[1:]))
+    return ctype
+
+def parse_content_disposition_header(value):
+    """ disposition-type *( ";" parameter )
+
+    """
+    disp_header = ContentDisposition()
+    if not value:
+        disp_header.defects.append(errors.HeaderMissingRequiredValue(
+            "Missing content disposition"))
+        return disp_header
+    try:
+        token, value = get_token(value)
+    except errors.HeaderParseError:
+        disp_header.defects.append(errors.InvalidHeaderDefect(
+            "Expected content disposition but found {!r}".format(value)))
+        _find_mime_parameters(disp_header, value)
+        return disp_header
+    disp_header.append(token)
+    disp_header.content_disposition = token.value.strip().lower()
+    if not value:
+        return disp_header
+    if value[0] != ';':
+        disp_header.defects.append(errors.InvalidHeaderDefect(
+            "Only parameters are valid after content disposition, but "
+            "found {!r}".format(value)))
+        _find_mime_parameters(disp_header, value)
+        return disp_header
+    disp_header.append(ValueTerminal(';', 'parameter-separator'))
+    disp_header.append(parse_mime_parameters(value[1:]))
+    return disp_header
+
+def parse_content_transfer_encoding_header(value):
+    """ mechanism
+
+    """
+    # We should probably validate the values, since the list is fixed.
+    cte_header = ContentTransferEncoding()
+    if not value:
+        cte_header.defects.append(errors.HeaderMissingRequiredValue(
+            "Missing content transfer encoding"))
+        return cte_header
+    try:
+        token, value = get_token(value)
+    except errors.HeaderParseError:
+        cte_header.defects.append(errors.InvalidHeaderDefect(
+            "Expected content transfer encoding but found {!r}".format(value)))
+    else:
+        cte_header.append(token)
+        cte_header.cte = token.value.strip().lower()
+    if not value:
+        return cte_header
+    while value:
+        cte_header.defects.append(errors.InvalidHeaderDefect(
+            "Extra text after content transfer encoding"))
+        if value[0] in PHRASE_ENDS:
+            cte_header.append(ValueTerminal(value[0], 'misplaced-special'))
+            value = value[1:]
+        else:
+            token, value = get_phrase(value)
+            cte_header.append(token)
+    return cte_header
+
+
+#
+# Header folding
+#
+# Header folding is complex, with lots of rules and corner cases.  The
+# following code does its best to obey the rules and handle the corner
+# cases, but you can be sure there are few bugs:)
+#
+# This folder generally canonicalizes as it goes, preferring the stringified
+# version of each token.  The tokens contain information that supports the
+# folder, including which tokens can be encoded in which ways.
+#
+# Folded text is accumulated in a simple list of strings ('lines'), each
+# one of which should be less than policy.max_line_length ('maxlen').
+#
+
+def _steal_trailing_WSP_if_exists(lines):
+    wsp = ''
+    if lines and lines[-1] and lines[-1][-1] in WSP:
+        wsp = lines[-1][-1]
+        lines[-1] = lines[-1][:-1]
+    return wsp
+
+def _refold_parse_tree(parse_tree, *, policy):
+    """Return string of contents of parse_tree folded according to RFC rules.
+
+    """
+    # max_line_length 0/None means no limit, ie: infinitely long.
+    maxlen = policy.max_line_length or sys.maxsize
+    encoding = 'utf-8' if policy.utf8 else 'us-ascii'
+    lines = ['']
+    last_ew = None
+    wrap_as_ew_blocked = 0
+    want_encoding = False
+    end_ew_not_allowed = Terminal('', 'wrap_as_ew_blocked')
+    parts = list(parse_tree)
+    while parts:
+        part = parts.pop(0)
+        if part is end_ew_not_allowed:
+            wrap_as_ew_blocked -= 1
+            continue
+        tstr = str(part)
+        if part.token_type == 'ptext' and set(tstr) & SPECIALS:
+            # Encode if tstr contains special characters.
+            want_encoding = True
+        try:
+            tstr.encode(encoding)
+            charset = encoding
+        except UnicodeEncodeError:
+            if any(isinstance(x, errors.UndecodableBytesDefect)
+                   for x in part.all_defects):
+                charset = 'unknown-8bit'
+            else:
+                # If policy.utf8 is false this should really be taken from a
+                # 'charset' property on the policy.
+                charset = 'utf-8'
+            want_encoding = True
+        if part.token_type == 'mime-parameters':
+            # Mime parameter folding (using RFC2231) is extra special.
+            _fold_mime_parameters(part, lines, maxlen, encoding)
+            continue
+        if want_encoding and not wrap_as_ew_blocked:
+            if not part.as_ew_allowed:
+                want_encoding = False
+                last_ew = None
+                if part.syntactic_break:
+                    encoded_part = part.fold(policy=policy)[:-len(policy.linesep)]
+                    if policy.linesep not in encoded_part:
+                        # It fits on a single line
+                        if len(encoded_part) > maxlen - len(lines[-1]):
+                            # But not on this one, so start a new one.
+                            newline = _steal_trailing_WSP_if_exists(lines)
+                            # XXX what if encoded_part has no leading FWS?
+                            lines.append(newline)
+                        lines[-1] += encoded_part
+                        continue
+                # Either this is not a major syntactic break, so we don't
+                # want it on a line by itself even if it fits, or it
+                # doesn't fit on a line by itself.  Either way, fall through
+                # to unpacking the subparts and wrapping them.
+            if not hasattr(part, 'encode'):
+                # It's not a Terminal, do each piece individually.
+                parts = list(part) + parts
+            else:
+                # It's a terminal, wrap it as an encoded word, possibly
+                # combining it with previously encoded words if allowed.
+                last_ew = _fold_as_ew(tstr, lines, maxlen, last_ew,
+                                      part.ew_combine_allowed, charset)
+            want_encoding = False
+            continue
+        if len(tstr) <= maxlen - len(lines[-1]):
+            lines[-1] += tstr
+            continue
+        # This part is too long to fit.  The RFC wants us to break at
+        # "major syntactic breaks", so unless we don't consider this
+        # to be one, check if it will fit on the next line by itself.
+        if (part.syntactic_break and
+                len(tstr) + 1 <= maxlen):
+            newline = _steal_trailing_WSP_if_exists(lines)
+            if newline or part.startswith_fws():
+                lines.append(newline + tstr)
+                last_ew = None
+                continue
+        if not hasattr(part, 'encode'):
+            # It's not a terminal, try folding the subparts.
+            newparts = list(part)
+            if not part.as_ew_allowed:
+                wrap_as_ew_blocked += 1
+                newparts.append(end_ew_not_allowed)
+            parts = newparts + parts
+            continue
+        if part.as_ew_allowed and not wrap_as_ew_blocked:
+            # It doesn't need CTE encoding, but encode it anyway so we can
+            # wrap it.
+            parts.insert(0, part)
+            want_encoding = True
+            continue
+        # We can't figure out how to wrap, it, so give up.
+        newline = _steal_trailing_WSP_if_exists(lines)
+        if newline or part.startswith_fws():
+            lines.append(newline + tstr)
+        else:
+            # We can't fold it onto the next line either...
+            lines[-1] += tstr
+    return policy.linesep.join(lines) + policy.linesep
+
+def _fold_as_ew(to_encode, lines, maxlen, last_ew, ew_combine_allowed, charset):
+    """Fold string to_encode into lines as encoded word, combining if allowed.
+    Return the new value for last_ew, or None if ew_combine_allowed is False.
+
+    If there is already an encoded word in the last line of lines (indicated by
+    a non-None value for last_ew) and ew_combine_allowed is true, decode the
+    existing ew, combine it with to_encode, and re-encode.  Otherwise, encode
+    to_encode.  In either case, split to_encode as necessary so that the
+    encoded segments fit within maxlen.
+
+    """
+    if last_ew is not None and ew_combine_allowed:
+        to_encode = str(
+            get_unstructured(lines[-1][last_ew:] + to_encode))
+        lines[-1] = lines[-1][:last_ew]
+    if to_encode[0] in WSP:
+        # We're joining this to non-encoded text, so don't encode
+        # the leading blank.
+        leading_wsp = to_encode[0]
+        to_encode = to_encode[1:]
+        if (len(lines[-1]) == maxlen):
+            lines.append(_steal_trailing_WSP_if_exists(lines))
+        lines[-1] += leading_wsp
+    trailing_wsp = ''
+    if to_encode[-1] in WSP:
+        # Likewise for the trailing space.
+        trailing_wsp = to_encode[-1]
+        to_encode = to_encode[:-1]
+    new_last_ew = len(lines[-1]) if last_ew is None else last_ew
+
+    encode_as = 'utf-8' if charset == 'us-ascii' else charset
+
+    # The RFC2047 chrome takes up 7 characters plus the length
+    # of the charset name.
+    chrome_len = len(encode_as) + 7
+
+    if (chrome_len + 1) >= maxlen:
+        raise errors.HeaderParseError(
+            "max_line_length is too small to fit an encoded word")
+
+    while to_encode:
+        remaining_space = maxlen - len(lines[-1])
+        text_space = remaining_space - chrome_len
+        if text_space <= 0:
+            lines.append(' ')
+            continue
+
+        to_encode_word = to_encode[:text_space]
+        encoded_word = _ew.encode(to_encode_word, charset=encode_as)
+        excess = len(encoded_word) - remaining_space
+        while excess > 0:
+            # Since the chunk to encode is guaranteed to fit into less than 100 characters,
+            # shrinking it by one at a time shouldn't take long.
+            to_encode_word = to_encode_word[:-1]
+            encoded_word = _ew.encode(to_encode_word, charset=encode_as)
+            excess = len(encoded_word) - remaining_space
+        lines[-1] += encoded_word
+        to_encode = to_encode[len(to_encode_word):]
+
+        if to_encode:
+            lines.append(' ')
+            new_last_ew = len(lines[-1])
+    lines[-1] += trailing_wsp
+    return new_last_ew if ew_combine_allowed else None
+
+def _fold_mime_parameters(part, lines, maxlen, encoding):
+    """Fold TokenList 'part' into the 'lines' list as mime parameters.
+
+    Using the decoded list of parameters and values, format them according to
+    the RFC rules, including using RFC2231 encoding if the value cannot be
+    expressed in 'encoding' and/or the parameter+value is too long to fit
+    within 'maxlen'.
+
+    """
+    # Special case for RFC2231 encoding: start from decoded values and use
+    # RFC2231 encoding iff needed.
+    #
+    # Note that the 1 and 2s being added to the length calculations are
+    # accounting for the possibly-needed spaces and semicolons we'll be adding.
+    #
+    for name, value in part.params:
+        # XXX What if this ';' puts us over maxlen the first time through the
+        # loop?  We should split the header value onto a newline in that case,
+        # but to do that we need to recognize the need earlier or reparse the
+        # header, so I'm going to ignore that bug for now.  It'll only put us
+        # one character over.
+        if not lines[-1].rstrip().endswith(';'):
+            lines[-1] += ';'
+        charset = encoding
+        error_handler = 'strict'
+        try:
+            value.encode(encoding)
+            encoding_required = False
+        except UnicodeEncodeError:
+            encoding_required = True
+            if utils._has_surrogates(value):
+                charset = 'unknown-8bit'
+                error_handler = 'surrogateescape'
+            else:
+                charset = 'utf-8'
+        if encoding_required:
+            encoded_value = urllib.parse.quote(
+                value, safe='', errors=error_handler)
+            tstr = "{}*={}''{}".format(name, charset, encoded_value)
+        else:
+            tstr = '{}={}'.format(name, quote_string(value))
+        if len(lines[-1]) + len(tstr) + 1 < maxlen:
+            lines[-1] = lines[-1] + ' ' + tstr
+            continue
+        elif len(tstr) + 2 <= maxlen:
+            lines.append(' ' + tstr)
+            continue
+        # We need multiple sections.  We are allowed to mix encoded and
+        # non-encoded sections, but we aren't going to.  We'll encode them all.
+        section = 0
+        extra_chrome = charset + "''"
+        while value:
+            chrome_len = len(name) + len(str(section)) + 3 + len(extra_chrome)
+            if maxlen <= chrome_len + 3:
+                # We need room for the leading blank, the trailing semicolon,
+                # and at least one character of the value.  If we don't
+                # have that, we'd be stuck, so in that case fall back to
+                # the RFC standard width.
+                maxlen = 78
+            splitpoint = maxchars = maxlen - chrome_len - 2
+            while True:
+                partial = value[:splitpoint]
+                encoded_value = urllib.parse.quote(
+                    partial, safe='', errors=error_handler)
+                if len(encoded_value) <= maxchars:
+                    break
+                splitpoint -= 1
+            lines.append(" {}*{}*={}{}".format(
+                name, section, extra_chrome, encoded_value))
+            extra_chrome = ''
+            section += 1
+            value = value[splitpoint:]
+            if value:
+                lines[-1] += ';'
diff --git a/contrib/tools/python3/src/Lib/email/_parseaddr.py b/contrib/tools/python3/src/Lib/email/_parseaddr.py
new file mode 100644
index 0000000000..c5a7b23193
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/_parseaddr.py
@@ -0,0 +1,553 @@
+# Copyright (C) 2002-2007 Python Software Foundation
+# Contact: email-sig@python.org
+
+"""Email address parsing code.
+
+Lifted directly from rfc822.py.  This should eventually be rewritten.
+"""
+
+__all__ = [
+    'mktime_tz',
+    'parsedate',
+    'parsedate_tz',
+    'quote',
+    ]
+
+import time, calendar
+
+SPACE = ' '
+EMPTYSTRING = ''
+COMMASPACE = ', '
+
+# Parse a date field
+_monthnames = ['jan', 'feb', 'mar', 'apr', 'may', 'jun', 'jul',
+               'aug', 'sep', 'oct', 'nov', 'dec',
+               'january', 'february', 'march', 'april', 'may', 'june', 'july',
+               'august', 'september', 'october', 'november', 'december']
+
+_daynames = ['mon', 'tue', 'wed', 'thu', 'fri', 'sat', 'sun']
+
+# The timezone table does not include the military time zones defined
+# in RFC822, other than Z.  According to RFC1123, the description in
+# RFC822 gets the signs wrong, so we can't rely on any such time
+# zones.  RFC1123 recommends that numeric timezone indicators be used
+# instead of timezone names.
+
+_timezones = {'UT':0, 'UTC':0, 'GMT':0, 'Z':0,
+              'AST': -400, 'ADT': -300,  # Atlantic (used in Canada)
+              'EST': -500, 'EDT': -400,  # Eastern
+              'CST': -600, 'CDT': -500,  # Central
+              'MST': -700, 'MDT': -600,  # Mountain
+              'PST': -800, 'PDT': -700   # Pacific
+              }
+
+
+def parsedate_tz(data):
+    """Convert a date string to a time tuple.
+
+    Accounts for military timezones.
+    """
+    res = _parsedate_tz(data)
+    if not res:
+        return
+    if res[9] is None:
+        res[9] = 0
+    return tuple(res)
+
+def _parsedate_tz(data):
+    """Convert date to extended time tuple.
+
+    The last (additional) element is the time zone offset in seconds, except if
+    the timezone was specified as -0000.  In that case the last element is
+    None.  This indicates a UTC timestamp that explicitly declaims knowledge of
+    the source timezone, as opposed to a +0000 timestamp that indicates the
+    source timezone really was UTC.
+
+    """
+    if not data:
+        return
+    data = data.split()
+    if not data:  # This happens for whitespace-only input.
+        return None
+    # The FWS after the comma after the day-of-week is optional, so search and
+    # adjust for this.
+    if data[0].endswith(',') or data[0].lower() in _daynames:
+        # There's a dayname here. Skip it
+        del data[0]
+    else:
+        i = data[0].rfind(',')
+        if i >= 0:
+            data[0] = data[0][i+1:]
+    if len(data) == 3: # RFC 850 date, deprecated
+        stuff = data[0].split('-')
+        if len(stuff) == 3:
+            data = stuff + data[1:]
+    if len(data) == 4:
+        s = data[3]
+        i = s.find('+')
+        if i == -1:
+            i = s.find('-')
+        if i > 0:
+            data[3:] = [s[:i], s[i:]]
+        else:
+            data.append('') # Dummy tz
+    if len(data) < 5:
+        return None
+    data = data[:5]
+    [dd, mm, yy, tm, tz] = data
+    mm = mm.lower()
+    if mm not in _monthnames:
+        dd, mm = mm, dd.lower()
+        if mm not in _monthnames:
+            return None
+    mm = _monthnames.index(mm) + 1
+    if mm > 12:
+        mm -= 12
+    if dd[-1] == ',':
+        dd = dd[:-1]
+    i = yy.find(':')
+    if i > 0:
+        yy, tm = tm, yy
+    if yy[-1] == ',':
+        yy = yy[:-1]
+    if not yy[0].isdigit():
+        yy, tz = tz, yy
+    if tm[-1] == ',':
+        tm = tm[:-1]
+    tm = tm.split(':')
+    if len(tm) == 2:
+        [thh, tmm] = tm
+        tss = '0'
+    elif len(tm) == 3:
+        [thh, tmm, tss] = tm
+    elif len(tm) == 1 and '.' in tm[0]:
+        # Some non-compliant MUAs use '.' to separate time elements.
+        tm = tm[0].split('.')
+        if len(tm) == 2:
+            [thh, tmm] = tm
+            tss = 0
+        elif len(tm) == 3:
+            [thh, tmm, tss] = tm
+        else:
+            return None
+    else:
+        return None
+    try:
+        yy = int(yy)
+        dd = int(dd)
+        thh = int(thh)
+        tmm = int(tmm)
+        tss = int(tss)
+    except ValueError:
+        return None
+    # Check for a yy specified in two-digit format, then convert it to the
+    # appropriate four-digit format, according to the POSIX standard. RFC 822
+    # calls for a two-digit yy, but RFC 2822 (which obsoletes RFC 822)
+    # mandates a 4-digit yy. For more information, see the documentation for
+    # the time module.
+    if yy < 100:
+        # The year is between 1969 and 1999 (inclusive).
+        if yy > 68:
+            yy += 1900
+        # The year is between 2000 and 2068 (inclusive).
+        else:
+            yy += 2000
+    tzoffset = None
+    tz = tz.upper()
+    if tz in _timezones:
+        tzoffset = _timezones[tz]
+    else:
+        try:
+            tzoffset = int(tz)
+        except ValueError:
+            pass
+        if tzoffset==0 and tz.startswith('-'):
+            tzoffset = None
+    # Convert a timezone offset into seconds ; -0500 -> -18000
+    if tzoffset:
+        if tzoffset < 0:
+            tzsign = -1
+            tzoffset = -tzoffset
+        else:
+            tzsign = 1
+        tzoffset = tzsign * ( (tzoffset//100)*3600 + (tzoffset % 100)*60)
+    # Daylight Saving Time flag is set to -1, since DST is unknown.
+    return [yy, mm, dd, thh, tmm, tss, 0, 1, -1, tzoffset]
+
+
+def parsedate(data):
+    """Convert a time string to a time tuple."""
+    t = parsedate_tz(data)
+    if isinstance(t, tuple):
+        return t[:9]
+    else:
+        return t
+
+
+def mktime_tz(data):
+    """Turn a 10-tuple as returned by parsedate_tz() into a POSIX timestamp."""
+    if data[9] is None:
+        # No zone info, so localtime is better assumption than GMT
+        return time.mktime(data[:8] + (-1,))
+    else:
+        t = calendar.timegm(data)
+        return t - data[9]
+
+
+def quote(str):
+    """Prepare string to be used in a quoted string.
+
+    Turns backslash and double quote characters into quoted pairs.  These
+    are the only characters that need to be quoted inside a quoted string.
+    Does not add the surrounding double quotes.
+    """
+    return str.replace('\\', '\\\\').replace('"', '\\"')
+
+
+class AddrlistClass:
+    """Address parser class by Ben Escoto.
+
+    To understand what this class does, it helps to have a copy of RFC 2822 in
+    front of you.
+
+    Note: this class interface is deprecated and may be removed in the future.
+    Use email.utils.AddressList instead.
+    """
+
+    def __init__(self, field):
+        """Initialize a new instance.
+
+        `field' is an unparsed address header field, containing
+        one or more addresses.
+        """
+        self.specials = '()<>@,:;.\"[]'
+        self.pos = 0
+        self.LWS = ' \t'
+        self.CR = '\r\n'
+        self.FWS = self.LWS + self.CR
+        self.atomends = self.specials + self.LWS + self.CR
+        # Note that RFC 2822 now specifies `.' as obs-phrase, meaning that it
+        # is obsolete syntax.  RFC 2822 requires that we recognize obsolete
+        # syntax, so allow dots in phrases.
+        self.phraseends = self.atomends.replace('.', '')
+        self.field = field
+        self.commentlist = []
+
+    def gotonext(self):
+        """Skip white space and extract comments."""
+        wslist = []
+        while self.pos < len(self.field):
+            if self.field[self.pos] in self.LWS + '\n\r':
+                if self.field[self.pos] not in '\n\r':
+                    wslist.append(self.field[self.pos])
+                self.pos += 1
+            elif self.field[self.pos] == '(':
+                self.commentlist.append(self.getcomment())
+            else:
+                break
+        return EMPTYSTRING.join(wslist)
+
+    def getaddrlist(self):
+        """Parse all addresses.
+
+        Returns a list containing all of the addresses.
+        """
+        result = []
+        while self.pos < len(self.field):
+            ad = self.getaddress()
+            if ad:
+                result += ad
+            else:
+                result.append(('', ''))
+        return result
+
+    def getaddress(self):
+        """Parse the next address."""
+        self.commentlist = []
+        self.gotonext()
+
+        oldpos = self.pos
+        oldcl = self.commentlist
+        plist = self.getphraselist()
+
+        self.gotonext()
+        returnlist = []
+
+        if self.pos >= len(self.field):
+            # Bad email address technically, no domain.
+            if plist:
+                returnlist = [(SPACE.join(self.commentlist), plist[0])]
+
+        elif self.field[self.pos] in '.@':
+            # email address is just an addrspec
+            # this isn't very efficient since we start over
+            self.pos = oldpos
+            self.commentlist = oldcl
+            addrspec = self.getaddrspec()
+            returnlist = [(SPACE.join(self.commentlist), addrspec)]
+
+        elif self.field[self.pos] == ':':
+            # address is a group
+            returnlist = []
+
+            fieldlen = len(self.field)
+            self.pos += 1
+            while self.pos < len(self.field):
+                self.gotonext()
+                if self.pos < fieldlen and self.field[self.pos] == ';':
+                    self.pos += 1
+                    break
+                returnlist = returnlist + self.getaddress()
+
+        elif self.field[self.pos] == '<':
+            # Address is a phrase then a route addr
+            routeaddr = self.getrouteaddr()
+
+            if self.commentlist:
+                returnlist = [(SPACE.join(plist) + ' (' +
+                               ' '.join(self.commentlist) + ')', routeaddr)]
+            else:
+                returnlist = [(SPACE.join(plist), routeaddr)]
+
+        else:
+            if plist:
+                returnlist = [(SPACE.join(self.commentlist), plist[0])]
+            elif self.field[self.pos] in self.specials:
+                self.pos += 1
+
+        self.gotonext()
+        if self.pos < len(self.field) and self.field[self.pos] == ',':
+            self.pos += 1
+        return returnlist
+
+    def getrouteaddr(self):
+        """Parse a route address (Return-path value).
+
+        This method just skips all the route stuff and returns the addrspec.
+        """
+        if self.field[self.pos] != '<':
+            return
+
+        expectroute = False
+        self.pos += 1
+        self.gotonext()
+        adlist = ''
+        while self.pos < len(self.field):
+            if expectroute:
+                self.getdomain()
+                expectroute = False
+            elif self.field[self.pos] == '>':
+                self.pos += 1
+                break
+            elif self.field[self.pos] == '@':
+                self.pos += 1
+                expectroute = True
+            elif self.field[self.pos] == ':':
+                self.pos += 1
+            else:
+                adlist = self.getaddrspec()
+                self.pos += 1
+                break
+            self.gotonext()
+
+        return adlist
+
+    def getaddrspec(self):
+        """Parse an RFC 2822 addr-spec."""
+        aslist = []
+
+        self.gotonext()
+        while self.pos < len(self.field):
+            preserve_ws = True
+            if self.field[self.pos] == '.':
+                if aslist and not aslist[-1].strip():
+                    aslist.pop()
+                aslist.append('.')
+                self.pos += 1
+                preserve_ws = False
+            elif self.field[self.pos] == '"':
+                aslist.append('"%s"' % quote(self.getquote()))
+            elif self.field[self.pos] in self.atomends:
+                if aslist and not aslist[-1].strip():
+                    aslist.pop()
+                break
+            else:
+                aslist.append(self.getatom())
+            ws = self.gotonext()
+            if preserve_ws and ws:
+                aslist.append(ws)
+
+        if self.pos >= len(self.field) or self.field[self.pos] != '@':
+            return EMPTYSTRING.join(aslist)
+
+        aslist.append('@')
+        self.pos += 1
+        self.gotonext()
+        domain = self.getdomain()
+        if not domain:
+            # Invalid domain, return an empty address instead of returning a
+            # local part to denote failed parsing.
+            return EMPTYSTRING
+        return EMPTYSTRING.join(aslist) + domain
+
+    def getdomain(self):
+        """Get the complete domain name from an address."""
+        sdlist = []
+        while self.pos < len(self.field):
+            if self.field[self.pos] in self.LWS:
+                self.pos += 1
+            elif self.field[self.pos] == '(':
+                self.commentlist.append(self.getcomment())
+            elif self.field[self.pos] == '[':
+                sdlist.append(self.getdomainliteral())
+            elif self.field[self.pos] == '.':
+                self.pos += 1
+                sdlist.append('.')
+            elif self.field[self.pos] == '@':
+                # bpo-34155: Don't parse domains with two `@` like
+                # `a@malicious.org@important.com`.
+                return EMPTYSTRING
+            elif self.field[self.pos] in self.atomends:
+                break
+            else:
+                sdlist.append(self.getatom())
+        return EMPTYSTRING.join(sdlist)
+
+    def getdelimited(self, beginchar, endchars, allowcomments=True):
+        """Parse a header fragment delimited by special characters.
+
+        `beginchar' is the start character for the fragment.
+        If self is not looking at an instance of `beginchar' then
+        getdelimited returns the empty string.
+
+        `endchars' is a sequence of allowable end-delimiting characters.
+        Parsing stops when one of these is encountered.
+
+        If `allowcomments' is non-zero, embedded RFC 2822 comments are allowed
+        within the parsed fragment.
+        """
+        if self.field[self.pos] != beginchar:
+            return ''
+
+        slist = ['']
+        quote = False
+        self.pos += 1
+        while self.pos < len(self.field):
+            if quote:
+                slist.append(self.field[self.pos])
+                quote = False
+            elif self.field[self.pos] in endchars:
+                self.pos += 1
+                break
+            elif allowcomments and self.field[self.pos] == '(':
+                slist.append(self.getcomment())
+                continue        # have already advanced pos from getcomment
+            elif self.field[self.pos] == '\\':
+                quote = True
+            else:
+                slist.append(self.field[self.pos])
+            self.pos += 1
+
+        return EMPTYSTRING.join(slist)
+
+    def getquote(self):
+        """Get a quote-delimited fragment from self's field."""
+        return self.getdelimited('"', '"\r', False)
+
+    def getcomment(self):
+        """Get a parenthesis-delimited fragment from self's field."""
+        return self.getdelimited('(', ')\r', True)
+
+    def getdomainliteral(self):
+        """Parse an RFC 2822 domain-literal."""
+        return '[%s]' % self.getdelimited('[', ']\r', False)
+
+    def getatom(self, atomends=None):
+        """Parse an RFC 2822 atom.
+
+        Optional atomends specifies a different set of end token delimiters
+        (the default is to use self.atomends).  This is used e.g. in
+        getphraselist() since phrase endings must not include the `.' (which
+        is legal in phrases)."""
+        atomlist = ['']
+        if atomends is None:
+            atomends = self.atomends
+
+        while self.pos < len(self.field):
+            if self.field[self.pos] in atomends:
+                break
+            else:
+                atomlist.append(self.field[self.pos])
+            self.pos += 1
+
+        return EMPTYSTRING.join(atomlist)
+
+    def getphraselist(self):
+        """Parse a sequence of RFC 2822 phrases.
+
+        A phrase is a sequence of words, which are in turn either RFC 2822
+        atoms or quoted-strings.  Phrases are canonicalized by squeezing all
+        runs of continuous whitespace into one space.
+        """
+        plist = []
+
+        while self.pos < len(self.field):
+            if self.field[self.pos] in self.FWS:
+                self.pos += 1
+            elif self.field[self.pos] == '"':
+                plist.append(self.getquote())
+            elif self.field[self.pos] == '(':
+                self.commentlist.append(self.getcomment())
+            elif self.field[self.pos] in self.phraseends:
+                break
+            else:
+                plist.append(self.getatom(self.phraseends))
+
+        return plist
+
+class AddressList(AddrlistClass):
+    """An AddressList encapsulates a list of parsed RFC 2822 addresses."""
+    def __init__(self, field):
+        AddrlistClass.__init__(self, field)
+        if field:
+            self.addresslist = self.getaddrlist()
+        else:
+            self.addresslist = []
+
+    def __len__(self):
+        return len(self.addresslist)
+
+    def __add__(self, other):
+        # Set union
+        newaddr = AddressList(None)
+        newaddr.addresslist = self.addresslist[:]
+        for x in other.addresslist:
+            if not x in self.addresslist:
+                newaddr.addresslist.append(x)
+        return newaddr
+
+    def __iadd__(self, other):
+        # Set union, in-place
+        for x in other.addresslist:
+            if not x in self.addresslist:
+                self.addresslist.append(x)
+        return self
+
+    def __sub__(self, other):
+        # Set difference
+        newaddr = AddressList(None)
+        for x in self.addresslist:
+            if not x in other.addresslist:
+                newaddr.addresslist.append(x)
+        return newaddr
+
+    def __isub__(self, other):
+        # Set difference, in-place
+        for x in other.addresslist:
+            if x in self.addresslist:
+                self.addresslist.remove(x)
+        return self
+
+    def __getitem__(self, index):
+        # Make indexing, slices, and 'in' work
+        return self.addresslist[index]
diff --git a/contrib/tools/python3/src/Lib/email/_policybase.py b/contrib/tools/python3/src/Lib/email/_policybase.py
new file mode 100644
index 0000000000..c9cbadd2a8
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/_policybase.py
@@ -0,0 +1,374 @@
+"""Policy framework for the email package.
+
+Allows fine grained feature control of how the package parses and emits data.
+"""
+
+import abc
+from email import header
+from email import charset as _charset
+from email.utils import _has_surrogates
+
+__all__ = [
+    'Policy',
+    'Compat32',
+    'compat32',
+    ]
+
+
+class _PolicyBase:
+
+    """Policy Object basic framework.
+
+    This class is useless unless subclassed.  A subclass should define
+    class attributes with defaults for any values that are to be
+    managed by the Policy object.  The constructor will then allow
+    non-default values to be set for these attributes at instance
+    creation time.  The instance will be callable, taking these same
+    attributes keyword arguments, and returning a new instance
+    identical to the called instance except for those values changed
+    by the keyword arguments.  Instances may be added, yielding new
+    instances with any non-default values from the right hand
+    operand overriding those in the left hand operand.  That is,
+
+        A + B == A(<non-default values of B>)
+
+    The repr of an instance can be used to reconstruct the object
+    if and only if the repr of the values can be used to reconstruct
+    those values.
+
+    """
+
+    def __init__(self, **kw):
+        """Create new Policy, possibly overriding some defaults.
+
+        See class docstring for a list of overridable attributes.
+
+        """
+        for name, value in kw.items():
+            if hasattr(self, name):
+                super(_PolicyBase,self).__setattr__(name, value)
+            else:
+                raise TypeError(
+                    "{!r} is an invalid keyword argument for {}".format(
+                        name, self.__class__.__name__))
+
+    def __repr__(self):
+        args = [ "{}={!r}".format(name, value)
+                 for name, value in self.__dict__.items() ]
+        return "{}({})".format(self.__class__.__name__, ', '.join(args))
+
+    def clone(self, **kw):
+        """Return a new instance with specified attributes changed.
+
+        The new instance has the same attribute values as the current object,
+        except for the changes passed in as keyword arguments.
+
+        """
+        newpolicy = self.__class__.__new__(self.__class__)
+        for attr, value in self.__dict__.items():
+            object.__setattr__(newpolicy, attr, value)
+        for attr, value in kw.items():
+            if not hasattr(self, attr):
+                raise TypeError(
+                    "{!r} is an invalid keyword argument for {}".format(
+                        attr, self.__class__.__name__))
+            object.__setattr__(newpolicy, attr, value)
+        return newpolicy
+
+    def __setattr__(self, name, value):
+        if hasattr(self, name):
+            msg = "{!r} object attribute {!r} is read-only"
+        else:
+            msg = "{!r} object has no attribute {!r}"
+        raise AttributeError(msg.format(self.__class__.__name__, name))
+
+    def __add__(self, other):
+        """Non-default values from right operand override those from left.
+
+        The object returned is a new instance of the subclass.
+
+        """
+        return self.clone(**other.__dict__)
+
+
+def _append_doc(doc, added_doc):
+    doc = doc.rsplit('\n', 1)[0]
+    added_doc = added_doc.split('\n', 1)[1]
+    return doc + '\n' + added_doc
+
+def _extend_docstrings(cls):
+    if cls.__doc__ and cls.__doc__.startswith('+'):
+        cls.__doc__ = _append_doc(cls.__bases__[0].__doc__, cls.__doc__)
+    for name, attr in cls.__dict__.items():
+        if attr.__doc__ and attr.__doc__.startswith('+'):
+            for c in (c for base in cls.__bases__ for c in base.mro()):
+                doc = getattr(getattr(c, name), '__doc__')
+                if doc:
+                    attr.__doc__ = _append_doc(doc, attr.__doc__)
+                    break
+    return cls
+
+
+class Policy(_PolicyBase, metaclass=abc.ABCMeta):
+
+    r"""Controls for how messages are interpreted and formatted.
+
+    Most of the classes and many of the methods in the email package accept
+    Policy objects as parameters.  A Policy object contains a set of values and
+    functions that control how input is interpreted and how output is rendered.
+    For example, the parameter 'raise_on_defect' controls whether or not an RFC
+    violation results in an error being raised or not, while 'max_line_length'
+    controls the maximum length of output lines when a Message is serialized.
+
+    Any valid attribute may be overridden when a Policy is created by passing
+    it as a keyword argument to the constructor.  Policy objects are immutable,
+    but a new Policy object can be created with only certain values changed by
+    calling the Policy instance with keyword arguments.  Policy objects can
+    also be added, producing a new Policy object in which the non-default
+    attributes set in the right hand operand overwrite those specified in the
+    left operand.
+
+    Settable attributes:
+
+    raise_on_defect     -- If true, then defects should be raised as errors.
+                           Default: False.
+
+    linesep             -- string containing the value to use as separation
+                           between output lines.  Default '\n'.
+
+    cte_type            -- Type of allowed content transfer encodings
+
+                           7bit  -- ASCII only
+                           8bit  -- Content-Transfer-Encoding: 8bit is allowed
+
+                           Default: 8bit.  Also controls the disposition of
+                           (RFC invalid) binary data in headers; see the
+                           documentation of the binary_fold method.
+
+    max_line_length     -- maximum length of lines, excluding 'linesep',
+                           during serialization.  None or 0 means no line
+                           wrapping is done.  Default is 78.
+
+    mangle_from_        -- a flag that, when True escapes From_ lines in the
+                           body of the message by putting a `>' in front of
+                           them. This is used when the message is being
+                           serialized by a generator. Default: True.
+
+    message_factory     -- the class to use to create new message objects.
+                           If the value is None, the default is Message.
+
+    """
+
+    raise_on_defect = False
+    linesep = '\n'
+    cte_type = '8bit'
+    max_line_length = 78
+    mangle_from_ = False
+    message_factory = None
+
+    def handle_defect(self, obj, defect):
+        """Based on policy, either raise defect or call register_defect.
+
+            handle_defect(obj, defect)
+
+        defect should be a Defect subclass, but in any case must be an
+        Exception subclass.  obj is the object on which the defect should be
+        registered if it is not raised.  If the raise_on_defect is True, the
+        defect is raised as an error, otherwise the object and the defect are
+        passed to register_defect.
+
+        This method is intended to be called by parsers that discover defects.
+        The email package parsers always call it with Defect instances.
+
+        """
+        if self.raise_on_defect:
+            raise defect
+        self.register_defect(obj, defect)
+
+    def register_defect(self, obj, defect):
+        """Record 'defect' on 'obj'.
+
+        Called by handle_defect if raise_on_defect is False.  This method is
+        part of the Policy API so that Policy subclasses can implement custom
+        defect handling.  The default implementation calls the append method of
+        the defects attribute of obj.  The objects used by the email package by
+        default that get passed to this method will always have a defects
+        attribute with an append method.
+
+        """
+        obj.defects.append(defect)
+
+    def header_max_count(self, name):
+        """Return the maximum allowed number of headers named 'name'.
+
+        Called when a header is added to a Message object.  If the returned
+        value is not 0 or None, and there are already a number of headers with
+        the name 'name' equal to the value returned, a ValueError is raised.
+
+        Because the default behavior of Message's __setitem__ is to append the
+        value to the list of headers, it is easy to create duplicate headers
+        without realizing it.  This method allows certain headers to be limited
+        in the number of instances of that header that may be added to a
+        Message programmatically.  (The limit is not observed by the parser,
+        which will faithfully produce as many headers as exist in the message
+        being parsed.)
+
+        The default implementation returns None for all header names.
+        """
+        return None
+
+    @abc.abstractmethod
+    def header_source_parse(self, sourcelines):
+        """Given a list of linesep terminated strings constituting the lines of
+        a single header, return the (name, value) tuple that should be stored
+        in the model.  The input lines should retain their terminating linesep
+        characters.  The lines passed in by the email package may contain
+        surrogateescaped binary data.
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def header_store_parse(self, name, value):
+        """Given the header name and the value provided by the application
+        program, return the (name, value) that should be stored in the model.
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def header_fetch_parse(self, name, value):
+        """Given the header name and the value from the model, return the value
+        to be returned to the application program that is requesting that
+        header.  The value passed in by the email package may contain
+        surrogateescaped binary data if the lines were parsed by a BytesParser.
+        The returned value should not contain any surrogateescaped data.
+
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def fold(self, name, value):
+        """Given the header name and the value from the model, return a string
+        containing linesep characters that implement the folding of the header
+        according to the policy controls.  The value passed in by the email
+        package may contain surrogateescaped binary data if the lines were
+        parsed by a BytesParser.  The returned value should not contain any
+        surrogateescaped data.
+
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def fold_binary(self, name, value):
+        """Given the header name and the value from the model, return binary
+        data containing linesep characters that implement the folding of the
+        header according to the policy controls.  The value passed in by the
+        email package may contain surrogateescaped binary data.
+
+        """
+        raise NotImplementedError
+
+
+@_extend_docstrings
+class Compat32(Policy):
+
+    """+
+    This particular policy is the backward compatibility Policy.  It
+    replicates the behavior of the email package version 5.1.
+    """
+
+    mangle_from_ = True
+
+    def _sanitize_header(self, name, value):
+        # If the header value contains surrogates, return a Header using
+        # the unknown-8bit charset to encode the bytes as encoded words.
+        if not isinstance(value, str):
+            # Assume it is already a header object
+            return value
+        if _has_surrogates(value):
+            return header.Header(value, charset=_charset.UNKNOWN8BIT,
+                                 header_name=name)
+        else:
+            return value
+
+    def header_source_parse(self, sourcelines):
+        """+
+        The name is parsed as everything up to the ':' and returned unmodified.
+        The value is determined by stripping leading whitespace off the
+        remainder of the first line, joining all subsequent lines together, and
+        stripping any trailing carriage return or linefeed characters.
+
+        """
+        name, value = sourcelines[0].split(':', 1)
+        value = value.lstrip(' \t') + ''.join(sourcelines[1:])
+        return (name, value.rstrip('\r\n'))
+
+    def header_store_parse(self, name, value):
+        """+
+        The name and value are returned unmodified.
+        """
+        return (name, value)
+
+    def header_fetch_parse(self, name, value):
+        """+
+        If the value contains binary data, it is converted into a Header object
+        using the unknown-8bit charset.  Otherwise it is returned unmodified.
+        """
+        return self._sanitize_header(name, value)
+
+    def fold(self, name, value):
+        """+
+        Headers are folded using the Header folding algorithm, which preserves
+        existing line breaks in the value, and wraps each resulting line to the
+        max_line_length.  Non-ASCII binary data are CTE encoded using the
+        unknown-8bit charset.
+
+        """
+        return self._fold(name, value, sanitize=True)
+
+    def fold_binary(self, name, value):
+        """+
+        Headers are folded using the Header folding algorithm, which preserves
+        existing line breaks in the value, and wraps each resulting line to the
+        max_line_length.  If cte_type is 7bit, non-ascii binary data is CTE
+        encoded using the unknown-8bit charset.  Otherwise the original source
+        header is used, with its existing line breaks and/or binary data.
+
+        """
+        folded = self._fold(name, value, sanitize=self.cte_type=='7bit')
+        return folded.encode('ascii', 'surrogateescape')
+
+    def _fold(self, name, value, sanitize):
+        parts = []
+        parts.append('%s: ' % name)
+        if isinstance(value, str):
+            if _has_surrogates(value):
+                if sanitize:
+                    h = header.Header(value,
+                                      charset=_charset.UNKNOWN8BIT,
+                                      header_name=name)
+                else:
+                    # If we have raw 8bit data in a byte string, we have no idea
+                    # what the encoding is.  There is no safe way to split this
+                    # string.  If it's ascii-subset, then we could do a normal
+                    # ascii split, but if it's multibyte then we could break the
+                    # string.  There's no way to know so the least harm seems to
+                    # be to not split the string and risk it being too long.
+                    parts.append(value)
+                    h = None
+            else:
+                h = header.Header(value, header_name=name)
+        else:
+            # Assume it is a Header-like object.
+            h = value
+        if h is not None:
+            # The Header class interprets a value of None for maxlinelen as the
+            # default value of 78, as recommended by RFC 2822.
+            maxlinelen = 0
+            if self.max_line_length is not None:
+                maxlinelen = self.max_line_length
+            parts.append(h.encode(linesep=self.linesep, maxlinelen=maxlinelen))
+        parts.append(self.linesep)
+        return ''.join(parts)
+
+
+compat32 = Compat32()
diff --git a/contrib/tools/python3/src/Lib/email/base64mime.py b/contrib/tools/python3/src/Lib/email/base64mime.py
new file mode 100644
index 0000000000..17f0818f6c
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/base64mime.py
@@ -0,0 +1,119 @@
+# Copyright (C) 2002-2007 Python Software Foundation
+# Author: Ben Gertzfield
+# Contact: email-sig@python.org
+
+"""Base64 content transfer encoding per RFCs 2045-2047.
+
+This module handles the content transfer encoding method defined in RFC 2045
+to encode arbitrary 8-bit data using the three 8-bit bytes in four 7-bit
+characters encoding known as Base64.
+
+It is used in the MIME standards for email to attach images, audio, and text
+using some 8-bit character sets to messages.
+
+This module provides an interface to encode and decode both headers and bodies
+with Base64 encoding.
+
+RFC 2045 defines a method for including character set information in an
+`encoded-word' in a header.  This method is commonly used for 8-bit real names
+in To:, From:, Cc:, etc. fields, as well as Subject: lines.
+
+This module does not do the line wrapping or end-of-line character conversion
+necessary for proper internationalized headers; it only does dumb encoding and
+decoding.  To deal with the various line wrapping issues, use the email.header
+module.
+"""
+
+__all__ = [
+    'body_decode',
+    'body_encode',
+    'decode',
+    'decodestring',
+    'header_encode',
+    'header_length',
+    ]
+
+
+from base64 import b64encode
+from binascii import b2a_base64, a2b_base64
+
+CRLF = '\r\n'
+NL = '\n'
+EMPTYSTRING = ''
+
+# See also Charset.py
+MISC_LEN = 7
+
+
+
+# Helpers
+def header_length(bytearray):
+    """Return the length of s when it is encoded with base64."""
+    groups_of_3, leftover = divmod(len(bytearray), 3)
+    # 4 bytes out for each 3 bytes (or nonzero fraction thereof) in.
+    n = groups_of_3 * 4
+    if leftover:
+        n += 4
+    return n
+
+
+
+def header_encode(header_bytes, charset='iso-8859-1'):
+    """Encode a single header line with Base64 encoding in a given charset.
+
+    charset names the character set to use to encode the header.  It defaults
+    to iso-8859-1.  Base64 encoding is defined in RFC 2045.
+    """
+    if not header_bytes:
+        return ""
+    if isinstance(header_bytes, str):
+        header_bytes = header_bytes.encode(charset)
+    encoded = b64encode(header_bytes).decode("ascii")
+    return '=?%s?b?%s?=' % (charset, encoded)
+
+
+
+def body_encode(s, maxlinelen=76, eol=NL):
+    r"""Encode a string with base64.
+
+    Each line will be wrapped at, at most, maxlinelen characters (defaults to
+    76 characters).
+
+    Each line of encoded text will end with eol, which defaults to "\n".  Set
+    this to "\r\n" if you will be using the result of this function directly
+    in an email.
+    """
+    if not s:
+        return s
+
+    encvec = []
+    max_unencoded = maxlinelen * 3 // 4
+    for i in range(0, len(s), max_unencoded):
+        # BAW: should encode() inherit b2a_base64()'s dubious behavior in
+        # adding a newline to the encoded string?
+        enc = b2a_base64(s[i:i + max_unencoded]).decode("ascii")
+        if enc.endswith(NL) and eol != NL:
+            enc = enc[:-1] + eol
+        encvec.append(enc)
+    return EMPTYSTRING.join(encvec)
+
+
+
+def decode(string):
+    """Decode a raw base64 string, returning a bytes object.
+
+    This function does not parse a full MIME header value encoded with
+    base64 (like =?iso-8859-1?b?bmloISBuaWgh?=) -- please use the high
+    level email.header class for that functionality.
+    """
+    if not string:
+        return bytes()
+    elif isinstance(string, str):
+        return a2b_base64(string.encode('raw-unicode-escape'))
+    else:
+        return a2b_base64(string)
+
+
+# For convenience and backwards compatibility w/ standard base64 module
+body_decode = decode
+decodestring = decode
diff --git a/contrib/tools/python3/src/Lib/email/charset.py b/contrib/tools/python3/src/Lib/email/charset.py
new file mode 100644
index 0000000000..d3d759ad91
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/charset.py
@@ -0,0 +1,404 @@
+# Copyright (C) 2001-2007 Python Software Foundation
+# Author: Ben Gertzfield, Barry Warsaw
+# Contact: email-sig@python.org
+
+__all__ = [
+    'Charset',
+    'add_alias',
+    'add_charset',
+    'add_codec',
+    ]
+
+from functools import partial
+
+import email.base64mime
+import email.quoprimime
+
+from email import errors
+from email.encoders import encode_7or8bit
+
+
+
+# Flags for types of header encodings
+QP          = 1 # Quoted-Printable
+BASE64      = 2 # Base64
+SHORTEST    = 3 # the shorter of QP and base64, but only for headers
+
+# In "=?charset?q?hello_world?=", the =?, ?q?, and ?= add up to 7
+RFC2047_CHROME_LEN = 7
+
+DEFAULT_CHARSET = 'us-ascii'
+UNKNOWN8BIT = 'unknown-8bit'
+EMPTYSTRING = ''
+
+
+
+# Defaults
+CHARSETS = {
+    # input        header enc  body enc output conv
+    'iso-8859-1':  (QP,        QP,      None),
+    'iso-8859-2':  (QP,        QP,      None),
+    'iso-8859-3':  (QP,        QP,      None),
+    'iso-8859-4':  (QP,        QP,      None),
+    # iso-8859-5 is Cyrillic, and not especially used
+    # iso-8859-6 is Arabic, also not particularly used
+    # iso-8859-7 is Greek, QP will not make it readable
+    # iso-8859-8 is Hebrew, QP will not make it readable
+    'iso-8859-9':  (QP,        QP,      None),
+    'iso-8859-10': (QP,        QP,      None),
+    # iso-8859-11 is Thai, QP will not make it readable
+    'iso-8859-13': (QP,        QP,      None),
+    'iso-8859-14': (QP,        QP,      None),
+    'iso-8859-15': (QP,        QP,      None),
+    'iso-8859-16': (QP,        QP,      None),
+    'windows-1252':(QP,        QP,      None),
+    'viscii':      (QP,        QP,      None),
+    'us-ascii':    (None,      None,    None),
+    'big5':        (BASE64,    BASE64,  None),
+    'gb2312':      (BASE64,    BASE64,  None),
+    'euc-jp':      (BASE64,    None,    'iso-2022-jp'),
+    'shift_jis':   (BASE64,    None,    'iso-2022-jp'),
+    'iso-2022-jp': (BASE64,    None,    None),
+    'koi8-r':      (BASE64,    BASE64,  None),
+    'utf-8':       (SHORTEST,  BASE64, 'utf-8'),
+    }
+
+# Aliases for other commonly-used names for character sets.  Map
+# them to the real ones used in email.
+ALIASES = {
+    'latin_1': 'iso-8859-1',
+    'latin-1': 'iso-8859-1',
+    'latin_2': 'iso-8859-2',
+    'latin-2': 'iso-8859-2',
+    'latin_3': 'iso-8859-3',
+    'latin-3': 'iso-8859-3',
+    'latin_4': 'iso-8859-4',
+    'latin-4': 'iso-8859-4',
+    'latin_5': 'iso-8859-9',
+    'latin-5': 'iso-8859-9',
+    'latin_6': 'iso-8859-10',
+    'latin-6': 'iso-8859-10',
+    'latin_7': 'iso-8859-13',
+    'latin-7': 'iso-8859-13',
+    'latin_8': 'iso-8859-14',
+    'latin-8': 'iso-8859-14',
+    'latin_9': 'iso-8859-15',
+    'latin-9': 'iso-8859-15',
+    'latin_10':'iso-8859-16',
+    'latin-10':'iso-8859-16',
+    'cp949':   'ks_c_5601-1987',
+    'euc_jp':  'euc-jp',
+    'euc_kr':  'euc-kr',
+    'ascii':   'us-ascii',
+    }
+
+
+# Map charsets to their Unicode codec strings.
+CODEC_MAP = {
+    'gb2312':      'eucgb2312_cn',
+    'big5':        'big5_tw',
+    # Hack: We don't want *any* conversion for stuff marked us-ascii, as all
+    # sorts of garbage might be sent to us in the guise of 7-bit us-ascii.
+    # Let that stuff pass through without conversion to/from Unicode.
+    'us-ascii':    None,
+    }
+
+
+
+# Convenience functions for extending the above mappings
+def add_charset(charset, header_enc=None, body_enc=None, output_charset=None):
+    """Add character set properties to the global registry.
+
+    charset is the input character set, and must be the canonical name of a
+    character set.
+
+    Optional header_enc and body_enc is either Charset.QP for
+    quoted-printable, Charset.BASE64 for base64 encoding, Charset.SHORTEST for
+    the shortest of qp or base64 encoding, or None for no encoding.  SHORTEST
+    is only valid for header_enc.  It describes how message headers and
+    message bodies in the input charset are to be encoded.  Default is no
+    encoding.
+
+    Optional output_charset is the character set that the output should be
+    in.  Conversions will proceed from input charset, to Unicode, to the
+    output charset when the method Charset.convert() is called.  The default
+    is to output in the same character set as the input.
+
+    Both input_charset and output_charset must have Unicode codec entries in
+    the module's charset-to-codec mapping; use add_codec(charset, codecname)
+    to add codecs the module does not know about.  See the codecs module's
+    documentation for more information.
+    """
+    if body_enc == SHORTEST:
+        raise ValueError('SHORTEST not allowed for body_enc')
+    CHARSETS[charset] = (header_enc, body_enc, output_charset)
+
+
+def add_alias(alias, canonical):
+    """Add a character set alias.
+
+    alias is the alias name, e.g. latin-1
+    canonical is the character set's canonical name, e.g. iso-8859-1
+    """
+    ALIASES[alias] = canonical
+
+
+def add_codec(charset, codecname):
+    """Add a codec that map characters in the given charset to/from Unicode.
+
+    charset is the canonical name of a character set.  codecname is the name
+    of a Python codec, as appropriate for the second argument to the unicode()
+    built-in, or to the encode() method of a Unicode string.
+    """
+    CODEC_MAP[charset] = codecname
+
+
+
+# Convenience function for encoding strings, taking into account
+# that they might be unknown-8bit (ie: have surrogate-escaped bytes)
+def _encode(string, codec):
+    if codec == UNKNOWN8BIT:
+        return string.encode('ascii', 'surrogateescape')
+    else:
+        return string.encode(codec)
+
+
+
+class Charset:
+    """Map character sets to their email properties.
+
+    This class provides information about the requirements imposed on email
+    for a specific character set.  It also provides convenience routines for
+    converting between character sets, given the availability of the
+    applicable codecs.  Given a character set, it will do its best to provide
+    information on how to use that character set in an email in an
+    RFC-compliant way.
+
+    Certain character sets must be encoded with quoted-printable or base64
+    when used in email headers or bodies.  Certain character sets must be
+    converted outright, and are not allowed in email.  Instances of this
+    module expose the following information about a character set:
+
+    input_charset: The initial character set specified.  Common aliases
+                   are converted to their `official' email names (e.g. latin_1
+                   is converted to iso-8859-1).  Defaults to 7-bit us-ascii.
+
+    header_encoding: If the character set must be encoded before it can be
+                     used in an email header, this attribute will be set to
+                     Charset.QP (for quoted-printable), Charset.BASE64 (for
+                     base64 encoding), or Charset.SHORTEST for the shortest of
+                     QP or BASE64 encoding.  Otherwise, it will be None.
+
+    body_encoding: Same as header_encoding, but describes the encoding for the
+                   mail message's body, which indeed may be different than the
+                   header encoding.  Charset.SHORTEST is not allowed for
+                   body_encoding.
+
+    output_charset: Some character sets must be converted before they can be
+                    used in email headers or bodies.  If the input_charset is
+                    one of them, this attribute will contain the name of the
+                    charset output will be converted to.  Otherwise, it will
+                    be None.
+
+    input_codec: The name of the Python codec used to convert the
+                 input_charset to Unicode.  If no conversion codec is
+                 necessary, this attribute will be None.
+
+    output_codec: The name of the Python codec used to convert Unicode
+                  to the output_charset.  If no conversion codec is necessary,
+                  this attribute will have the same value as the input_codec.
+    """
+    def __init__(self, input_charset=DEFAULT_CHARSET):
+        # RFC 2046, $4.1.2 says charsets are not case sensitive.  We coerce to
+        # unicode because its .lower() is locale insensitive.  If the argument
+        # is already a unicode, we leave it at that, but ensure that the
+        # charset is ASCII, as the standard (RFC XXX) requires.
+        try:
+            if isinstance(input_charset, str):
+                input_charset.encode('ascii')
+            else:
+                input_charset = str(input_charset, 'ascii')
+        except UnicodeError:
+            raise errors.CharsetError(input_charset)
+        input_charset = input_charset.lower()
+        # Set the input charset after filtering through the aliases
+        self.input_charset = ALIASES.get(input_charset, input_charset)
+        # We can try to guess which encoding and conversion to use by the
+        # charset_map dictionary.  Try that first, but let the user override
+        # it.
+        henc, benc, conv = CHARSETS.get(self.input_charset,
+                                        (SHORTEST, BASE64, None))
+        if not conv:
+            conv = self.input_charset
+        # Set the attributes, allowing the arguments to override the default.
+        self.header_encoding = henc
+        self.body_encoding = benc
+        self.output_charset = ALIASES.get(conv, conv)
+        # Now set the codecs.  If one isn't defined for input_charset,
+        # guess and try a Unicode codec with the same name as input_codec.
+        self.input_codec = CODEC_MAP.get(self.input_charset,
+                                         self.input_charset)
+        self.output_codec = CODEC_MAP.get(self.output_charset,
+                                          self.output_charset)
+
+    def __repr__(self):
+        return self.input_charset.lower()
+
+    def __eq__(self, other):
+        return str(self) == str(other).lower()
+
+    def get_body_encoding(self):
+        """Return the content-transfer-encoding used for body encoding.
+
+        This is either the string `quoted-printable' or `base64' depending on
+        the encoding used, or it is a function in which case you should call
+        the function with a single argument, the Message object being
+        encoded.  The function should then set the Content-Transfer-Encoding
+        header itself to whatever is appropriate.
+
+        Returns "quoted-printable" if self.body_encoding is QP.
+        Returns "base64" if self.body_encoding is BASE64.
+        Returns conversion function otherwise.
+        """
+        assert self.body_encoding != SHORTEST
+        if self.body_encoding == QP:
+            return 'quoted-printable'
+        elif self.body_encoding == BASE64:
+            return 'base64'
+        else:
+            return encode_7or8bit
+
+    def get_output_charset(self):
+        """Return the output character set.
+
+        This is self.output_charset if that is not None, otherwise it is
+        self.input_charset.
+        """
+        return self.output_charset or self.input_charset
+
+    def header_encode(self, string):
+        """Header-encode a string by converting it first to bytes.
+
+        The type of encoding (base64 or quoted-printable) will be based on
+        this charset's `header_encoding`.
+
+        :param string: A unicode string for the header.  It must be possible
+            to encode this string to bytes using the character set's
+            output codec.
+        :return: The encoded string, with RFC 2047 chrome.
+        """
+        codec = self.output_codec or 'us-ascii'
+        header_bytes = _encode(string, codec)
+        # 7bit/8bit encodings return the string unchanged (modulo conversions)
+        encoder_module = self._get_encoder(header_bytes)
+        if encoder_module is None:
+            return string
+        return encoder_module.header_encode(header_bytes, codec)
+
+    def header_encode_lines(self, string, maxlengths):
+        """Header-encode a string by converting it first to bytes.
+
+        This is similar to `header_encode()` except that the string is fit
+        into maximum line lengths as given by the argument.
+
+        :param string: A unicode string for the header.  It must be possible
+            to encode this string to bytes using the character set's
+            output codec.
+        :param maxlengths: Maximum line length iterator.  Each element
+            returned from this iterator will provide the next maximum line
+            length.  This parameter is used as an argument to built-in next()
+            and should never be exhausted.  The maximum line lengths should
+            not count the RFC 2047 chrome.  These line lengths are only a
+            hint; the splitter does the best it can.
+        :return: Lines of encoded strings, each with RFC 2047 chrome.
+        """
+        # See which encoding we should use.
+        codec = self.output_codec or 'us-ascii'
+        header_bytes = _encode(string, codec)
+        encoder_module = self._get_encoder(header_bytes)
+        encoder = partial(encoder_module.header_encode, charset=codec)
+        # Calculate the number of characters that the RFC 2047 chrome will
+        # contribute to each line.
+        charset = self.get_output_charset()
+        extra = len(charset) + RFC2047_CHROME_LEN
+        # Now comes the hard part.  We must encode bytes but we can't split on
+        # bytes because some character sets are variable length and each
+        # encoded word must stand on its own.  So the problem is you have to
+        # encode to bytes to figure out this word's length, but you must split
+        # on characters.  This causes two problems: first, we don't know how
+        # many octets a specific substring of unicode characters will get
+        # encoded to, and second, we don't know how many ASCII characters
+        # those octets will get encoded to.  Unless we try it.  Which seems
+        # inefficient.  In the interest of being correct rather than fast (and
+        # in the hope that there will be few encoded headers in any such
+        # message), brute force it. :(
+        lines = []
+        current_line = []
+        maxlen = next(maxlengths) - extra
+        for character in string:
+            current_line.append(character)
+            this_line = EMPTYSTRING.join(current_line)
+            length = encoder_module.header_length(_encode(this_line, charset))
+            if length > maxlen:
+                # This last character doesn't fit so pop it off.
+                current_line.pop()
+                # Does nothing fit on the first line?
+                if not lines and not current_line:
+                    lines.append(None)
+                else:
+                    separator = (' ' if lines else '')
+                    joined_line = EMPTYSTRING.join(current_line)
+                    header_bytes = _encode(joined_line, codec)
+                    lines.append(encoder(header_bytes))
+                current_line = [character]
+                maxlen = next(maxlengths) - extra
+        joined_line = EMPTYSTRING.join(current_line)
+        header_bytes = _encode(joined_line, codec)
+        lines.append(encoder(header_bytes))
+        return lines
+
+    def _get_encoder(self, header_bytes):
+        if self.header_encoding == BASE64:
+            return email.base64mime
+        elif self.header_encoding == QP:
+            return email.quoprimime
+        elif self.header_encoding == SHORTEST:
+            len64 = email.base64mime.header_length(header_bytes)
+            lenqp = email.quoprimime.header_length(header_bytes)
+            if len64 < lenqp:
+                return email.base64mime
+            else:
+                return email.quoprimime
+        else:
+            return None
+
+    def body_encode(self, string):
+        """Body-encode a string by converting it first to bytes.
+
+        The type of encoding (base64 or quoted-printable) will be based on
+        self.body_encoding.  If body_encoding is None, we assume the
+        output charset is a 7bit encoding, so re-encoding the decoded
+        string using the ascii codec produces the correct string version
+        of the content.
+        """
+        if not string:
+            return string
+        if self.body_encoding is BASE64:
+            if isinstance(string, str):
+                string = string.encode(self.output_charset)
+            return email.base64mime.body_encode(string)
+        elif self.body_encoding is QP:
+            # quopromime.body_encode takes a string, but operates on it as if
+            # it were a list of byte codes.  For a (minimal) history on why
+            # this is so, see changeset 0cf700464177.  To correctly encode a
+            # character set, then, we must turn it into pseudo bytes via the
+            # latin1 charset, which will encode any byte as a single code point
+            # between 0 and 255, which is what body_encode is expecting.
+            if isinstance(string, str):
+                string = string.encode(self.output_charset)
+            string = string.decode('latin1')
+            return email.quoprimime.body_encode(string)
+        else:
+            if isinstance(string, str):
+                string = string.encode(self.output_charset).decode('ascii')
+            return string
diff --git a/contrib/tools/python3/src/Lib/email/contentmanager.py b/contrib/tools/python3/src/Lib/email/contentmanager.py
new file mode 100644
index 0000000000..fcf278dbcc
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/contentmanager.py
@@ -0,0 +1,248 @@
+import binascii
+import email.charset
+import email.message
+import email.errors
+from email import quoprimime
+
+class ContentManager:
+
+    def __init__(self):
+        self.get_handlers = {}
+        self.set_handlers = {}
+
+    def add_get_handler(self, key, handler):
+        self.get_handlers[key] = handler
+
+    def get_content(self, msg, *args, **kw):
+        content_type = msg.get_content_type()
+        if content_type in self.get_handlers:
+            return self.get_handlers[content_type](msg, *args, **kw)
+        maintype = msg.get_content_maintype()
+        if maintype in self.get_handlers:
+            return self.get_handlers[maintype](msg, *args, **kw)
+        if '' in self.get_handlers:
+            return self.get_handlers[''](msg, *args, **kw)
+        raise KeyError(content_type)
+
+    def add_set_handler(self, typekey, handler):
+        self.set_handlers[typekey] = handler
+
+    def set_content(self, msg, obj, *args, **kw):
+        if msg.get_content_maintype() == 'multipart':
+            # XXX: is this error a good idea or not?  We can remove it later,
+            # but we can't add it later, so do it for now.
+            raise TypeError("set_content not valid on multipart")
+        handler = self._find_set_handler(msg, obj)
+        msg.clear_content()
+        handler(msg, obj, *args, **kw)
+
+    def _find_set_handler(self, msg, obj):
+        full_path_for_error = None
+        for typ in type(obj).__mro__:
+            if typ in self.set_handlers:
+                return self.set_handlers[typ]
+            qname = typ.__qualname__
+            modname = getattr(typ, '__module__', '')
+            full_path = '.'.join((modname, qname)) if modname else qname
+            if full_path_for_error is None:
+                full_path_for_error = full_path
+            if full_path in self.set_handlers:
+                return self.set_handlers[full_path]
+            if qname in self.set_handlers:
+                return self.set_handlers[qname]
+            name = typ.__name__
+            if name in self.set_handlers:
+                return self.set_handlers[name]
+        if None in self.set_handlers:
+            return self.set_handlers[None]
+        raise KeyError(full_path_for_error)
+
+
+raw_data_manager = ContentManager()
+
+
+def get_text_content(msg, errors='replace'):
+    content = msg.get_payload(decode=True)
+    charset = msg.get_param('charset', 'ASCII')
+    return content.decode(charset, errors=errors)
+raw_data_manager.add_get_handler('text', get_text_content)
+
+
+def get_non_text_content(msg):
+    return msg.get_payload(decode=True)
+for maintype in 'audio image video application'.split():
+    raw_data_manager.add_get_handler(maintype, get_non_text_content)
+
+
+def get_message_content(msg):
+    return msg.get_payload(0)
+for subtype in 'rfc822 external-body'.split():
+    raw_data_manager.add_get_handler('message/'+subtype, get_message_content)
+
+
+def get_and_fixup_unknown_message_content(msg):
+    # If we don't understand a message subtype, we are supposed to treat it as
+    # if it were application/octet-stream, per
+    # tools.ietf.org/html/rfc2046#section-5.2.4.  Feedparser doesn't do that,
+    # so do our best to fix things up.  Note that it is *not* appropriate to
+    # model message/partial content as Message objects, so they are handled
+    # here as well.  (How to reassemble them is out of scope for this comment :)
+    return bytes(msg.get_payload(0))
+raw_data_manager.add_get_handler('message',
+                                 get_and_fixup_unknown_message_content)
+
+
+def _prepare_set(msg, maintype, subtype, headers):
+    msg['Content-Type'] = '/'.join((maintype, subtype))
+    if headers:
+        if not hasattr(headers[0], 'name'):
+            mp = msg.policy
+            headers = [mp.header_factory(*mp.header_source_parse([header]))
+                       for header in headers]
+        try:
+            for header in headers:
+                if header.defects:
+                    raise header.defects[0]
+                msg[header.name] = header
+        except email.errors.HeaderDefect as exc:
+            raise ValueError("Invalid header: {}".format(
+                                header.fold(policy=msg.policy))) from exc
+
+
+def _finalize_set(msg, disposition, filename, cid, params):
+    if disposition is None and filename is not None:
+        disposition = 'attachment'
+    if disposition is not None:
+        msg['Content-Disposition'] = disposition
+    if filename is not None:
+        msg.set_param('filename',
+                      filename,
+                      header='Content-Disposition',
+                      replace=True)
+    if cid is not None:
+        msg['Content-ID'] = cid
+    if params is not None:
+        for key, value in params.items():
+            msg.set_param(key, value)
+
+
+# XXX: This is a cleaned-up version of base64mime.body_encode (including a bug
+# fix in the calculation of unencoded_bytes_per_line).  It would be nice to
+# drop both this and quoprimime.body_encode in favor of enhanced binascii
+# routines that accepted a max_line_length parameter.
+def _encode_base64(data, max_line_length):
+    encoded_lines = []
+    unencoded_bytes_per_line = max_line_length // 4 * 3
+    for i in range(0, len(data), unencoded_bytes_per_line):
+        thisline = data[i:i+unencoded_bytes_per_line]
+        encoded_lines.append(binascii.b2a_base64(thisline).decode('ascii'))
+    return ''.join(encoded_lines)
+
+
+def _encode_text(string, charset, cte, policy):
+    lines = string.encode(charset).splitlines()
+    linesep = policy.linesep.encode('ascii')
+    def embedded_body(lines): return linesep.join(lines) + linesep
+    def normal_body(lines): return b'\n'.join(lines) + b'\n'
+    if cte is None:
+        # Use heuristics to decide on the "best" encoding.
+        if max((len(x) for x in lines), default=0) <= policy.max_line_length:
+            try:
+                return '7bit', normal_body(lines).decode('ascii')
+            except UnicodeDecodeError:
+                pass
+            if policy.cte_type == '8bit':
+                return '8bit', normal_body(lines).decode('ascii', 'surrogateescape')
+        sniff = embedded_body(lines[:10])
+        sniff_qp = quoprimime.body_encode(sniff.decode('latin-1'),
+                                          policy.max_line_length)
+        sniff_base64 = binascii.b2a_base64(sniff)
+        # This is a little unfair to qp; it includes lineseps, base64 doesn't.
+        if len(sniff_qp) > len(sniff_base64):
+            cte = 'base64'
+        else:
+            cte = 'quoted-printable'
+            if len(lines) <= 10:
+                return cte, sniff_qp
+    if cte == '7bit':
+        data = normal_body(lines).decode('ascii')
+    elif cte == '8bit':
+        data = normal_body(lines).decode('ascii', 'surrogateescape')
+    elif cte == 'quoted-printable':
+        data = quoprimime.body_encode(normal_body(lines).decode('latin-1'),
+                                      policy.max_line_length)
+    elif cte == 'base64':
+        data = _encode_base64(embedded_body(lines), policy.max_line_length)
+    else:
+        raise ValueError("Unknown content transfer encoding {}".format(cte))
+    return cte, data
+
+
+def set_text_content(msg, string, subtype="plain", charset='utf-8', cte=None,
+                     disposition=None, filename=None, cid=None,
+                     params=None, headers=None):
+    _prepare_set(msg, 'text', subtype, headers)
+    cte, payload = _encode_text(string, charset, cte, msg.policy)
+    msg.set_payload(payload)
+    msg.set_param('charset',
+                  email.charset.ALIASES.get(charset, charset),
+                  replace=True)
+    msg['Content-Transfer-Encoding'] = cte
+    _finalize_set(msg, disposition, filename, cid, params)
+raw_data_manager.add_set_handler(str, set_text_content)
+
+
+def set_message_content(msg, message, subtype="rfc822", cte=None,
+                       disposition=None, filename=None, cid=None,
+                       params=None, headers=None):
+    if subtype == 'partial':
+        raise ValueError("message/partial is not supported for Message objects")
+    if subtype == 'rfc822':
+        if cte not in (None, '7bit', '8bit', 'binary'):
+            # http://tools.ietf.org/html/rfc2046#section-5.2.1 mandate.
+            raise ValueError(
+                "message/rfc822 parts do not support cte={}".format(cte))
+        # 8bit will get coerced on serialization if policy.cte_type='7bit'.  We
+        # may end up claiming 8bit when it isn't needed, but the only negative
+        # result of that should be a gateway that needs to coerce to 7bit
+        # having to look through the whole embedded message to discover whether
+        # or not it actually has to do anything.
+        cte = '8bit' if cte is None else cte
+    elif subtype == 'external-body':
+        if cte not in (None, '7bit'):
+            # http://tools.ietf.org/html/rfc2046#section-5.2.3 mandate.
+            raise ValueError(
+                "message/external-body parts do not support cte={}".format(cte))
+        cte = '7bit'
+    elif cte is None:
+        # http://tools.ietf.org/html/rfc2046#section-5.2.4 says all future
+        # subtypes should be restricted to 7bit, so assume that.
+        cte = '7bit'
+    _prepare_set(msg, 'message', subtype, headers)
+    msg.set_payload([message])
+    msg['Content-Transfer-Encoding'] = cte
+    _finalize_set(msg, disposition, filename, cid, params)
+raw_data_manager.add_set_handler(email.message.Message, set_message_content)
+
+
+def set_bytes_content(msg, data, maintype, subtype, cte='base64',
+                     disposition=None, filename=None, cid=None,
+                     params=None, headers=None):
+    _prepare_set(msg, maintype, subtype, headers)
+    if cte == 'base64':
+        data = _encode_base64(data, max_line_length=msg.policy.max_line_length)
+    elif cte == 'quoted-printable':
+        # XXX: quoprimime.body_encode won't encode newline characters in data,
+        # so we can't use it.  This means max_line_length is ignored.  Another
+        # bug to fix later.  (Note: encoders.quopri is broken on line ends.)
+        data = binascii.b2a_qp(data, istext=False, header=False, quotetabs=True)
+        data = data.decode('ascii')
+    elif cte == '7bit':
+        data = data.decode('ascii')
+    elif cte in ('8bit', 'binary'):
+        data = data.decode('ascii', 'surrogateescape')
+    msg.set_payload(data)
+    msg['Content-Transfer-Encoding'] = cte
+    _finalize_set(msg, disposition, filename, cid, params)
+for typ in (bytes, bytearray, memoryview):
+    raw_data_manager.add_set_handler(typ, set_bytes_content)
diff --git a/contrib/tools/python3/src/Lib/email/encoders.py b/contrib/tools/python3/src/Lib/email/encoders.py
new file mode 100644
index 0000000000..0a66acb624
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/encoders.py
@@ -0,0 +1,69 @@
+# Copyright (C) 2001-2006 Python Software Foundation
+# Author: Barry Warsaw
+# Contact: email-sig@python.org
+
+"""Encodings and related functions."""
+
+__all__ = [
+    'encode_7or8bit',
+    'encode_base64',
+    'encode_noop',
+    'encode_quopri',
+    ]
+
+
+from base64 import encodebytes as _bencode
+from quopri import encodestring as _encodestring
+
+
+
+def _qencode(s):
+    enc = _encodestring(s, quotetabs=True)
+    # Must encode spaces, which quopri.encodestring() doesn't do
+    return enc.replace(b' ', b'=20')
+
+
+def encode_base64(msg):
+    """Encode the message's payload in Base64.
+
+    Also, add an appropriate Content-Transfer-Encoding header.
+    """
+    orig = msg.get_payload(decode=True)
+    encdata = str(_bencode(orig), 'ascii')
+    msg.set_payload(encdata)
+    msg['Content-Transfer-Encoding'] = 'base64'
+
+
+
+def encode_quopri(msg):
+    """Encode the message's payload in quoted-printable.
+
+    Also, add an appropriate Content-Transfer-Encoding header.
+    """
+    orig = msg.get_payload(decode=True)
+    encdata = _qencode(orig)
+    msg.set_payload(encdata)
+    msg['Content-Transfer-Encoding'] = 'quoted-printable'
+
+
+
+def encode_7or8bit(msg):
+    """Set the Content-Transfer-Encoding header to 7bit or 8bit."""
+    orig = msg.get_payload(decode=True)
+    if orig is None:
+        # There's no payload.  For backwards compatibility we use 7bit
+        msg['Content-Transfer-Encoding'] = '7bit'
+        return
+    # We play a trick to make this go fast.  If decoding from ASCII succeeds,
+    # we know the data must be 7bit, otherwise treat it as 8bit.
+    try:
+        orig.decode('ascii')
+    except UnicodeError:
+        msg['Content-Transfer-Encoding'] = '8bit'
+    else:
+        msg['Content-Transfer-Encoding'] = '7bit'
+
+
+
+def encode_noop(msg):
+    """Do nothing."""
diff --git a/contrib/tools/python3/src/Lib/email/errors.py b/contrib/tools/python3/src/Lib/email/errors.py
new file mode 100644
index 0000000000..d28a680010
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/errors.py
@@ -0,0 +1,110 @@
+# Copyright (C) 2001-2006 Python Software Foundation
+# Author: Barry Warsaw
+# Contact: email-sig@python.org
+
+"""email package exception classes."""
+
+
+class MessageError(Exception):
+    """Base class for errors in the email package."""
+
+
+class MessageParseError(MessageError):
+    """Base class for message parsing errors."""
+
+
+class HeaderParseError(MessageParseError):
+    """Error while parsing headers."""
+
+
+class BoundaryError(MessageParseError):
+    """Couldn't find terminating boundary."""
+
+
+class MultipartConversionError(MessageError, TypeError):
+    """Conversion to a multipart is prohibited."""
+
+
+class CharsetError(MessageError):
+    """An illegal charset was given."""
+
+
+# These are parsing defects which the parser was able to work around.
+class MessageDefect(ValueError):
+    """Base class for a message defect."""
+
+    def __init__(self, line=None):
+        if line is not None:
+            super().__init__(line)
+        self.line = line
+
+class NoBoundaryInMultipartDefect(MessageDefect):
+    """A message claimed to be a multipart but had no boundary parameter."""
+
+class StartBoundaryNotFoundDefect(MessageDefect):
+    """The claimed start boundary was never found."""
+
+class CloseBoundaryNotFoundDefect(MessageDefect):
+    """A start boundary was found, but not the corresponding close boundary."""
+
+class FirstHeaderLineIsContinuationDefect(MessageDefect):
+    """A message had a continuation line as its first header line."""
+
+class MisplacedEnvelopeHeaderDefect(MessageDefect):
+    """A 'Unix-from' header was found in the middle of a header block."""
+
+class MissingHeaderBodySeparatorDefect(MessageDefect):
+    """Found line with no leading whitespace and no colon before blank line."""
+# XXX: backward compatibility, just in case (it was never emitted).
+MalformedHeaderDefect = MissingHeaderBodySeparatorDefect
+
+class MultipartInvariantViolationDefect(MessageDefect):
+    """A message claimed to be a multipart but no subparts were found."""
+
+class InvalidMultipartContentTransferEncodingDefect(MessageDefect):
+    """An invalid content transfer encoding was set on the multipart itself."""
+
+class UndecodableBytesDefect(MessageDefect):
+    """Header contained bytes that could not be decoded"""
+
+class InvalidBase64PaddingDefect(MessageDefect):
+    """base64 encoded sequence had an incorrect length"""
+
+class InvalidBase64CharactersDefect(MessageDefect):
+    """base64 encoded sequence had characters not in base64 alphabet"""
+
+class InvalidBase64LengthDefect(MessageDefect):
+    """base64 encoded sequence had invalid length (1 mod 4)"""
+
+# These errors are specific to header parsing.
+
+class HeaderDefect(MessageDefect):
+    """Base class for a header defect."""
+
+    def __init__(self, *args, **kw):
+        super().__init__(*args, **kw)
+
+class InvalidHeaderDefect(HeaderDefect):
+    """Header is not valid, message gives details."""
+
+class HeaderMissingRequiredValue(HeaderDefect):
+    """A header that must have a value had none"""
+
+class NonPrintableDefect(HeaderDefect):
+    """ASCII characters outside the ascii-printable range found"""
+
+    def __init__(self, non_printables):
+        super().__init__(non_printables)
+        self.non_printables = non_printables
+
+    def __str__(self):
+        return ("the following ASCII non-printables found in header: "
+            "{}".format(self.non_printables))
+
+class ObsoleteHeaderDefect(HeaderDefect):
+    """Header uses syntax declared obsolete by RFC 5322"""
+
+class NonASCIILocalPartDefect(HeaderDefect):
+    """local_part contains non-ASCII characters"""
+    # This defect only occurs during unicode parsing, not when
+    # parsing messages decoded from binary.
diff --git a/contrib/tools/python3/src/Lib/email/feedparser.py b/contrib/tools/python3/src/Lib/email/feedparser.py
new file mode 100644
index 0000000000..97d3f5144d
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/feedparser.py
@@ -0,0 +1,536 @@
+# Copyright (C) 2004-2006 Python Software Foundation
+# Authors: Baxter, Wouters and Warsaw
+# Contact: email-sig@python.org
+
+"""FeedParser - An email feed parser.
+
+The feed parser implements an interface for incrementally parsing an email
+message, line by line.  This has advantages for certain applications, such as
+those reading email messages off a socket.
+
+FeedParser.feed() is the primary interface for pushing new data into the
+parser.  It returns when there's nothing more it can do with the available
+data.  When you have no more data to push into the parser, call .close().
+This completes the parsing and returns the root message object.
+
+The other advantage of this parser is that it will never raise a parsing
+exception.  Instead, when it finds something unexpected, it adds a 'defect' to
+the current message.  Defects are just instances that live on the message
+object's .defects attribute.
+"""
+
+__all__ = ['FeedParser', 'BytesFeedParser']
+
+import re
+
+from email import errors
+from email._policybase import compat32
+from collections import deque
+from io import StringIO
+
+NLCRE = re.compile(r'\r\n|\r|\n')
+NLCRE_bol = re.compile(r'(\r\n|\r|\n)')
+NLCRE_eol = re.compile(r'(\r\n|\r|\n)\Z')
+NLCRE_crack = re.compile(r'(\r\n|\r|\n)')
+# RFC 2822 $3.6.8 Optional fields.  ftext is %d33-57 / %d59-126, Any character
+# except controls, SP, and ":".
+headerRE = re.compile(r'^(From |[\041-\071\073-\176]*:|[\t ])')
+EMPTYSTRING = ''
+NL = '\n'
+
+NeedMoreData = object()
+
+
+
+class BufferedSubFile(object):
+    """A file-ish object that can have new data loaded into it.
+
+    You can also push and pop line-matching predicates onto a stack.  When the
+    current predicate matches the current line, a false EOF response
+    (i.e. empty string) is returned instead.  This lets the parser adhere to a
+    simple abstraction -- it parses until EOF closes the current message.
+    """
+    def __init__(self):
+        # Text stream of the last partial line pushed into this object.
+        # See issue 22233 for why this is a text stream and not a list.
+        self._partial = StringIO(newline='')
+        # A deque of full, pushed lines
+        self._lines = deque()
+        # The stack of false-EOF checking predicates.
+        self._eofstack = []
+        # A flag indicating whether the file has been closed or not.
+        self._closed = False
+
+    def push_eof_matcher(self, pred):
+        self._eofstack.append(pred)
+
+    def pop_eof_matcher(self):
+        return self._eofstack.pop()
+
+    def close(self):
+        # Don't forget any trailing partial line.
+        self._partial.seek(0)
+        self.pushlines(self._partial.readlines())
+        self._partial.seek(0)
+        self._partial.truncate()
+        self._closed = True
+
+    def readline(self):
+        if not self._lines:
+            if self._closed:
+                return ''
+            return NeedMoreData
+        # Pop the line off the stack and see if it matches the current
+        # false-EOF predicate.
+        line = self._lines.popleft()
+        # RFC 2046, section 5.1.2 requires us to recognize outer level
+        # boundaries at any level of inner nesting.  Do this, but be sure it's
+        # in the order of most to least nested.
+        for ateof in reversed(self._eofstack):
+            if ateof(line):
+                # We're at the false EOF.  But push the last line back first.
+                self._lines.appendleft(line)
+                return ''
+        return line
+
+    def unreadline(self, line):
+        # Let the consumer push a line back into the buffer.
+        assert line is not NeedMoreData
+        self._lines.appendleft(line)
+
+    def push(self, data):
+        """Push some new data into this object."""
+        self._partial.write(data)
+        if '\n' not in data and '\r' not in data:
+            # No new complete lines, wait for more.
+            return
+
+        # Crack into lines, preserving the linesep characters.
+        self._partial.seek(0)
+        parts = self._partial.readlines()
+        self._partial.seek(0)
+        self._partial.truncate()
+
+        # If the last element of the list does not end in a newline, then treat
+        # it as a partial line.  We only check for '\n' here because a line
+        # ending with '\r' might be a line that was split in the middle of a
+        # '\r\n' sequence (see bugs 1555570 and 1721862).
+        if not parts[-1].endswith('\n'):
+            self._partial.write(parts.pop())
+        self.pushlines(parts)
+
+    def pushlines(self, lines):
+        self._lines.extend(lines)
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        line = self.readline()
+        if line == '':
+            raise StopIteration
+        return line
+
+
+
+class FeedParser:
+    """A feed-style parser of email."""
+
+    def __init__(self, _factory=None, *, policy=compat32):
+        """_factory is called with no arguments to create a new message obj
+
+        The policy keyword specifies a policy object that controls a number of
+        aspects of the parser's operation.  The default policy maintains
+        backward compatibility.
+
+        """
+        self.policy = policy
+        self._old_style_factory = False
+        if _factory is None:
+            if policy.message_factory is None:
+                from email.message import Message
+                self._factory = Message
+            else:
+                self._factory = policy.message_factory
+        else:
+            self._factory = _factory
+            try:
+                _factory(policy=self.policy)
+            except TypeError:
+                # Assume this is an old-style factory
+                self._old_style_factory = True
+        self._input = BufferedSubFile()
+        self._msgstack = []
+        self._parse = self._parsegen().__next__
+        self._cur = None
+        self._last = None
+        self._headersonly = False
+
+    # Non-public interface for supporting Parser's headersonly flag
+    def _set_headersonly(self):
+        self._headersonly = True
+
+    def feed(self, data):
+        """Push more data into the parser."""
+        self._input.push(data)
+        self._call_parse()
+
+    def _call_parse(self):
+        try:
+            self._parse()
+        except StopIteration:
+            pass
+
+    def close(self):
+        """Parse all remaining data and return the root message object."""
+        self._input.close()
+        self._call_parse()
+        root = self._pop_message()
+        assert not self._msgstack
+        # Look for final set of defects
+        if root.get_content_maintype() == 'multipart' \
+               and not root.is_multipart():
+            defect = errors.MultipartInvariantViolationDefect()
+            self.policy.handle_defect(root, defect)
+        return root
+
+    def _new_message(self):
+        if self._old_style_factory:
+            msg = self._factory()
+        else:
+            msg = self._factory(policy=self.policy)
+        if self._cur and self._cur.get_content_type() == 'multipart/digest':
+            msg.set_default_type('message/rfc822')
+        if self._msgstack:
+            self._msgstack[-1].attach(msg)
+        self._msgstack.append(msg)
+        self._cur = msg
+        self._last = msg
+
+    def _pop_message(self):
+        retval = self._msgstack.pop()
+        if self._msgstack:
+            self._cur = self._msgstack[-1]
+        else:
+            self._cur = None
+        return retval
+
+    def _parsegen(self):
+        # Create a new message and start by parsing headers.
+        self._new_message()
+        headers = []
+        # Collect the headers, searching for a line that doesn't match the RFC
+        # 2822 header or continuation pattern (including an empty line).
+        for line in self._input:
+            if line is NeedMoreData:
+                yield NeedMoreData
+                continue
+            if not headerRE.match(line):
+                # If we saw the RFC defined header/body separator
+                # (i.e. newline), just throw it away. Otherwise the line is
+                # part of the body so push it back.
+                if not NLCRE.match(line):
+                    defect = errors.MissingHeaderBodySeparatorDefect()
+                    self.policy.handle_defect(self._cur, defect)
+                    self._input.unreadline(line)
+                break
+            headers.append(line)
+        # Done with the headers, so parse them and figure out what we're
+        # supposed to see in the body of the message.
+        self._parse_headers(headers)
+        # Headers-only parsing is a backwards compatibility hack, which was
+        # necessary in the older parser, which could raise errors.  All
+        # remaining lines in the input are thrown into the message body.
+        if self._headersonly:
+            lines = []
+            while True:
+                line = self._input.readline()
+                if line is NeedMoreData:
+                    yield NeedMoreData
+                    continue
+                if line == '':
+                    break
+                lines.append(line)
+            self._cur.set_payload(EMPTYSTRING.join(lines))
+            return
+        if self._cur.get_content_type() == 'message/delivery-status':
+            # message/delivery-status contains blocks of headers separated by
+            # a blank line.  We'll represent each header block as a separate
+            # nested message object, but the processing is a bit different
+            # than standard message/* types because there is no body for the
+            # nested messages.  A blank line separates the subparts.
+            while True:
+                self._input.push_eof_matcher(NLCRE.match)
+                for retval in self._parsegen():
+                    if retval is NeedMoreData:
+                        yield NeedMoreData
+                        continue
+                    break
+                msg = self._pop_message()
+                # We need to pop the EOF matcher in order to tell if we're at
+                # the end of the current file, not the end of the last block
+                # of message headers.
+                self._input.pop_eof_matcher()
+                # The input stream must be sitting at the newline or at the
+                # EOF.  We want to see if we're at the end of this subpart, so
+                # first consume the blank line, then test the next line to see
+                # if we're at this subpart's EOF.
+                while True:
+                    line = self._input.readline()
+                    if line is NeedMoreData:
+                        yield NeedMoreData
+                        continue
+                    break
+                while True:
+                    line = self._input.readline()
+                    if line is NeedMoreData:
+                        yield NeedMoreData
+                        continue
+                    break
+                if line == '':
+                    break
+                # Not at EOF so this is a line we're going to need.
+                self._input.unreadline(line)
+            return
+        if self._cur.get_content_maintype() == 'message':
+            # The message claims to be a message/* type, then what follows is
+            # another RFC 2822 message.
+            for retval in self._parsegen():
+                if retval is NeedMoreData:
+                    yield NeedMoreData
+                    continue
+                break
+            self._pop_message()
+            return
+        if self._cur.get_content_maintype() == 'multipart':
+            boundary = self._cur.get_boundary()
+            if boundary is None:
+                # The message /claims/ to be a multipart but it has not
+                # defined a boundary.  That's a problem which we'll handle by
+                # reading everything until the EOF and marking the message as
+                # defective.
+                defect = errors.NoBoundaryInMultipartDefect()
+                self.policy.handle_defect(self._cur, defect)
+                lines = []
+                for line in self._input:
+                    if line is NeedMoreData:
+                        yield NeedMoreData
+                        continue
+                    lines.append(line)
+                self._cur.set_payload(EMPTYSTRING.join(lines))
+                return
+            # Make sure a valid content type was specified per RFC 2045:6.4.
+            if (str(self._cur.get('content-transfer-encoding', '8bit')).lower()
+                    not in ('7bit', '8bit', 'binary')):
+                defect = errors.InvalidMultipartContentTransferEncodingDefect()
+                self.policy.handle_defect(self._cur, defect)
+            # Create a line match predicate which matches the inter-part
+            # boundary as well as the end-of-multipart boundary.  Don't push
+            # this onto the input stream until we've scanned past the
+            # preamble.
+            separator = '--' + boundary
+            boundaryre = re.compile(
+                '(?P<sep>' + re.escape(separator) +
+                r')(?P<end>--)?(?P<ws>[ \t]*)(?P<linesep>\r\n|\r|\n)?$')
+            capturing_preamble = True
+            preamble = []
+            linesep = False
+            close_boundary_seen = False
+            while True:
+                line = self._input.readline()
+                if line is NeedMoreData:
+                    yield NeedMoreData
+                    continue
+                if line == '':
+                    break
+                mo = boundaryre.match(line)
+                if mo:
+                    # If we're looking at the end boundary, we're done with
+                    # this multipart.  If there was a newline at the end of
+                    # the closing boundary, then we need to initialize the
+                    # epilogue with the empty string (see below).
+                    if mo.group('end'):
+                        close_boundary_seen = True
+                        linesep = mo.group('linesep')
+                        break
+                    # We saw an inter-part boundary.  Were we in the preamble?
+                    if capturing_preamble:
+                        if preamble:
+                            # According to RFC 2046, the last newline belongs
+                            # to the boundary.
+                            lastline = preamble[-1]
+                            eolmo = NLCRE_eol.search(lastline)
+                            if eolmo:
+                                preamble[-1] = lastline[:-len(eolmo.group(0))]
+                            self._cur.preamble = EMPTYSTRING.join(preamble)
+                        capturing_preamble = False
+                        self._input.unreadline(line)
+                        continue
+                    # We saw a boundary separating two parts.  Consume any
+                    # multiple boundary lines that may be following.  Our
+                    # interpretation of RFC 2046 BNF grammar does not produce
+                    # body parts within such double boundaries.
+                    while True:
+                        line = self._input.readline()
+                        if line is NeedMoreData:
+                            yield NeedMoreData
+                            continue
+                        mo = boundaryre.match(line)
+                        if not mo:
+                            self._input.unreadline(line)
+                            break
+                    # Recurse to parse this subpart; the input stream points
+                    # at the subpart's first line.
+                    self._input.push_eof_matcher(boundaryre.match)
+                    for retval in self._parsegen():
+                        if retval is NeedMoreData:
+                            yield NeedMoreData
+                            continue
+                        break
+                    # Because of RFC 2046, the newline preceding the boundary
+                    # separator actually belongs to the boundary, not the
+                    # previous subpart's payload (or epilogue if the previous
+                    # part is a multipart).
+                    if self._last.get_content_maintype() == 'multipart':
+                        epilogue = self._last.epilogue
+                        if epilogue == '':
+                            self._last.epilogue = None
+                        elif epilogue is not None:
+                            mo = NLCRE_eol.search(epilogue)
+                            if mo:
+                                end = len(mo.group(0))
+                                self._last.epilogue = epilogue[:-end]
+                    else:
+                        payload = self._last._payload
+                        if isinstance(payload, str):
+                            mo = NLCRE_eol.search(payload)
+                            if mo:
+                                payload = payload[:-len(mo.group(0))]
+                                self._last._payload = payload
+                    self._input.pop_eof_matcher()
+                    self._pop_message()
+                    # Set the multipart up for newline cleansing, which will
+                    # happen if we're in a nested multipart.
+                    self._last = self._cur
+                else:
+                    # I think we must be in the preamble
+                    assert capturing_preamble
+                    preamble.append(line)
+            # We've seen either the EOF or the end boundary.  If we're still
+            # capturing the preamble, we never saw the start boundary.  Note
+            # that as a defect and store the captured text as the payload.
+            if capturing_preamble:
+                defect = errors.StartBoundaryNotFoundDefect()
+                self.policy.handle_defect(self._cur, defect)
+                self._cur.set_payload(EMPTYSTRING.join(preamble))
+                epilogue = []
+                for line in self._input:
+                    if line is NeedMoreData:
+                        yield NeedMoreData
+                        continue
+                self._cur.epilogue = EMPTYSTRING.join(epilogue)
+                return
+            # If we're not processing the preamble, then we might have seen
+            # EOF without seeing that end boundary...that is also a defect.
+            if not close_boundary_seen:
+                defect = errors.CloseBoundaryNotFoundDefect()
+                self.policy.handle_defect(self._cur, defect)
+                return
+            # Everything from here to the EOF is epilogue.  If the end boundary
+            # ended in a newline, we'll need to make sure the epilogue isn't
+            # None
+            if linesep:
+                epilogue = ['']
+            else:
+                epilogue = []
+            for line in self._input:
+                if line is NeedMoreData:
+                    yield NeedMoreData
+                    continue
+                epilogue.append(line)
+            # Any CRLF at the front of the epilogue is not technically part of
+            # the epilogue.  Also, watch out for an empty string epilogue,
+            # which means a single newline.
+            if epilogue:
+                firstline = epilogue[0]
+                bolmo = NLCRE_bol.match(firstline)
+                if bolmo:
+                    epilogue[0] = firstline[len(bolmo.group(0)):]
+            self._cur.epilogue = EMPTYSTRING.join(epilogue)
+            return
+        # Otherwise, it's some non-multipart type, so the entire rest of the
+        # file contents becomes the payload.
+        lines = []
+        for line in self._input:
+            if line is NeedMoreData:
+                yield NeedMoreData
+                continue
+            lines.append(line)
+        self._cur.set_payload(EMPTYSTRING.join(lines))
+
+    def _parse_headers(self, lines):
+        # Passed a list of lines that make up the headers for the current msg
+        lastheader = ''
+        lastvalue = []
+        for lineno, line in enumerate(lines):
+            # Check for continuation
+            if line[0] in ' \t':
+                if not lastheader:
+                    # The first line of the headers was a continuation.  This
+                    # is illegal, so let's note the defect, store the illegal
+                    # line, and ignore it for purposes of headers.
+                    defect = errors.FirstHeaderLineIsContinuationDefect(line)
+                    self.policy.handle_defect(self._cur, defect)
+                    continue
+                lastvalue.append(line)
+                continue
+            if lastheader:
+                self._cur.set_raw(*self.policy.header_source_parse(lastvalue))
+                lastheader, lastvalue = '', []
+            # Check for envelope header, i.e. unix-from
+            if line.startswith('From '):
+                if lineno == 0:
+                    # Strip off the trailing newline
+                    mo = NLCRE_eol.search(line)
+                    if mo:
+                        line = line[:-len(mo.group(0))]
+                    self._cur.set_unixfrom(line)
+                    continue
+                elif lineno == len(lines) - 1:
+                    # Something looking like a unix-from at the end - it's
+                    # probably the first line of the body, so push back the
+                    # line and stop.
+                    self._input.unreadline(line)
+                    return
+                else:
+                    # Weirdly placed unix-from line.  Note this as a defect
+                    # and ignore it.
+                    defect = errors.MisplacedEnvelopeHeaderDefect(line)
+                    self._cur.defects.append(defect)
+                    continue
+            # Split the line on the colon separating field name from value.
+            # There will always be a colon, because if there wasn't the part of
+            # the parser that calls us would have started parsing the body.
+            i = line.find(':')
+
+            # If the colon is on the start of the line the header is clearly
+            # malformed, but we might be able to salvage the rest of the
+            # message. Track the error but keep going.
+            if i == 0:
+                defect = errors.InvalidHeaderDefect("Missing header name.")
+                self._cur.defects.append(defect)
+                continue
+
+            assert i>0, "_parse_headers fed line with no : and no leading WS"
+            lastheader = line[:i]
+            lastvalue = [line]
+        # Done with all the lines, so handle the last header.
+        if lastheader:
+            self._cur.set_raw(*self.policy.header_source_parse(lastvalue))
+
+
+class BytesFeedParser(FeedParser):
+    """Like FeedParser, but feed accepts bytes."""
+
+    def feed(self, data):
+        super().feed(data.decode('ascii', 'surrogateescape'))
diff --git a/contrib/tools/python3/src/Lib/email/generator.py b/contrib/tools/python3/src/Lib/email/generator.py
new file mode 100644
index 0000000000..c9b121624e
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/generator.py
@@ -0,0 +1,512 @@
+# Copyright (C) 2001-2010 Python Software Foundation
+# Author: Barry Warsaw
+# Contact: email-sig@python.org
+
+"""Classes to generate plain text from a message object tree."""
+
+__all__ = ['Generator', 'DecodedGenerator', 'BytesGenerator']
+
+import re
+import sys
+import time
+import random
+
+from copy import deepcopy
+from io import StringIO, BytesIO
+from email.utils import _has_surrogates
+
+UNDERSCORE = '_'
+NL = '\n'  # XXX: no longer used by the code below.
+
+NLCRE = re.compile(r'\r\n|\r|\n')
+fcre = re.compile(r'^From ', re.MULTILINE)
+
+
+
+class Generator:
+    """Generates output from a Message object tree.
+
+    This basic generator writes the message to the given file object as plain
+    text.
+    """
+    #
+    # Public interface
+    #
+
+    def __init__(self, outfp, mangle_from_=None, maxheaderlen=None, *,
+                 policy=None):
+        """Create the generator for message flattening.
+
+        outfp is the output file-like object for writing the message to.  It
+        must have a write() method.
+
+        Optional mangle_from_ is a flag that, when True (the default if policy
+        is not set), escapes From_ lines in the body of the message by putting
+        a `>' in front of them.
+
+        Optional maxheaderlen specifies the longest length for a non-continued
+        header.  When a header line is longer (in characters, with tabs
+        expanded to 8 spaces) than maxheaderlen, the header will split as
+        defined in the Header class.  Set maxheaderlen to zero to disable
+        header wrapping.  The default is 78, as recommended (but not required)
+        by RFC 2822.
+
+        The policy keyword specifies a policy object that controls a number of
+        aspects of the generator's operation.  If no policy is specified,
+        the policy associated with the Message object passed to the
+        flatten method is used.
+
+        """
+
+        if mangle_from_ is None:
+            mangle_from_ = True if policy is None else policy.mangle_from_
+        self._fp = outfp
+        self._mangle_from_ = mangle_from_
+        self.maxheaderlen = maxheaderlen
+        self.policy = policy
+
+    def write(self, s):
+        # Just delegate to the file object
+        self._fp.write(s)
+
+    def flatten(self, msg, unixfrom=False, linesep=None):
+        r"""Print the message object tree rooted at msg to the output file
+        specified when the Generator instance was created.
+
+        unixfrom is a flag that forces the printing of a Unix From_ delimiter
+        before the first object in the message tree.  If the original message
+        has no From_ delimiter, a `standard' one is crafted.  By default, this
+        is False to inhibit the printing of any From_ delimiter.
+
+        Note that for subobjects, no From_ line is printed.
+
+        linesep specifies the characters used to indicate a new line in
+        the output.  The default value is determined by the policy specified
+        when the Generator instance was created or, if none was specified,
+        from the policy associated with the msg.
+
+        """
+        # We use the _XXX constants for operating on data that comes directly
+        # from the msg, and _encoded_XXX constants for operating on data that
+        # has already been converted (to bytes in the BytesGenerator) and
+        # inserted into a temporary buffer.
+        policy = msg.policy if self.policy is None else self.policy
+        if linesep is not None:
+            policy = policy.clone(linesep=linesep)
+        if self.maxheaderlen is not None:
+            policy = policy.clone(max_line_length=self.maxheaderlen)
+        self._NL = policy.linesep
+        self._encoded_NL = self._encode(self._NL)
+        self._EMPTY = ''
+        self._encoded_EMPTY = self._encode(self._EMPTY)
+        # Because we use clone (below) when we recursively process message
+        # subparts, and because clone uses the computed policy (not None),
+        # submessages will automatically get set to the computed policy when
+        # they are processed by this code.
+        old_gen_policy = self.policy
+        old_msg_policy = msg.policy
+        try:
+            self.policy = policy
+            msg.policy = policy
+            if unixfrom:
+                ufrom = msg.get_unixfrom()
+                if not ufrom:
+                    ufrom = 'From nobody ' + time.ctime(time.time())
+                self.write(ufrom + self._NL)
+            self._write(msg)
+        finally:
+            self.policy = old_gen_policy
+            msg.policy = old_msg_policy
+
+    def clone(self, fp):
+        """Clone this generator with the exact same options."""
+        return self.__class__(fp,
+                              self._mangle_from_,
+                              None, # Use policy setting, which we've adjusted
+                              policy=self.policy)
+
+    #
+    # Protected interface - undocumented ;/
+    #
+
+    # Note that we use 'self.write' when what we are writing is coming from
+    # the source, and self._fp.write when what we are writing is coming from a
+    # buffer (because the Bytes subclass has already had a chance to transform
+    # the data in its write method in that case).  This is an entirely
+    # pragmatic split determined by experiment; we could be more general by
+    # always using write and having the Bytes subclass write method detect when
+    # it has already transformed the input; but, since this whole thing is a
+    # hack anyway this seems good enough.
+
+    def _new_buffer(self):
+        # BytesGenerator overrides this to return BytesIO.
+        return StringIO()
+
+    def _encode(self, s):
+        # BytesGenerator overrides this to encode strings to bytes.
+        return s
+
+    def _write_lines(self, lines):
+        # We have to transform the line endings.
+        if not lines:
+            return
+        lines = NLCRE.split(lines)
+        for line in lines[:-1]:
+            self.write(line)
+            self.write(self._NL)
+        if lines[-1]:
+            self.write(lines[-1])
+        # XXX logic tells me this else should be needed, but the tests fail
+        # with it and pass without it.  (NLCRE.split ends with a blank element
+        # if and only if there was a trailing newline.)
+        #else:
+        #    self.write(self._NL)
+
+    def _write(self, msg):
+        # We can't write the headers yet because of the following scenario:
+        # say a multipart message includes the boundary string somewhere in
+        # its body.  We'd have to calculate the new boundary /before/ we write
+        # the headers so that we can write the correct Content-Type:
+        # parameter.
+        #
+        # The way we do this, so as to make the _handle_*() methods simpler,
+        # is to cache any subpart writes into a buffer.  The we write the
+        # headers and the buffer contents.  That way, subpart handlers can
+        # Do The Right Thing, and can still modify the Content-Type: header if
+        # necessary.
+        oldfp = self._fp
+        try:
+            self._munge_cte = None
+            self._fp = sfp = self._new_buffer()
+            self._dispatch(msg)
+        finally:
+            self._fp = oldfp
+            munge_cte = self._munge_cte
+            del self._munge_cte
+        # If we munged the cte, copy the message again and re-fix the CTE.
+        if munge_cte:
+            msg = deepcopy(msg)
+            # Preserve the header order if the CTE header already exists.
+            if msg.get('content-transfer-encoding') is None:
+                msg['Content-Transfer-Encoding'] = munge_cte[0]
+            else:
+                msg.replace_header('content-transfer-encoding', munge_cte[0])
+            msg.replace_header('content-type', munge_cte[1])
+        # Write the headers.  First we see if the message object wants to
+        # handle that itself.  If not, we'll do it generically.
+        meth = getattr(msg, '_write_headers', None)
+        if meth is None:
+            self._write_headers(msg)
+        else:
+            meth(self)
+        self._fp.write(sfp.getvalue())
+
+    def _dispatch(self, msg):
+        # Get the Content-Type: for the message, then try to dispatch to
+        # self._handle_<maintype>_<subtype>().  If there's no handler for the
+        # full MIME type, then dispatch to self._handle_<maintype>().  If
+        # that's missing too, then dispatch to self._writeBody().
+        main = msg.get_content_maintype()
+        sub = msg.get_content_subtype()
+        specific = UNDERSCORE.join((main, sub)).replace('-', '_')
+        meth = getattr(self, '_handle_' + specific, None)
+        if meth is None:
+            generic = main.replace('-', '_')
+            meth = getattr(self, '_handle_' + generic, None)
+            if meth is None:
+                meth = self._writeBody
+        meth(msg)
+
+    #
+    # Default handlers
+    #
+
+    def _write_headers(self, msg):
+        for h, v in msg.raw_items():
+            self.write(self.policy.fold(h, v))
+        # A blank line always separates headers from body
+        self.write(self._NL)
+
+    #
+    # Handlers for writing types and subtypes
+    #
+
+    def _handle_text(self, msg):
+        payload = msg.get_payload()
+        if payload is None:
+            return
+        if not isinstance(payload, str):
+            raise TypeError('string payload expected: %s' % type(payload))
+        if _has_surrogates(msg._payload):
+            charset = msg.get_param('charset')
+            if charset is not None:
+                # XXX: This copy stuff is an ugly hack to avoid modifying the
+                # existing message.
+                msg = deepcopy(msg)
+                del msg['content-transfer-encoding']
+                msg.set_payload(payload, charset)
+                payload = msg.get_payload()
+                self._munge_cte = (msg['content-transfer-encoding'],
+                                   msg['content-type'])
+        if self._mangle_from_:
+            payload = fcre.sub('>From ', payload)
+        self._write_lines(payload)
+
+    # Default body handler
+    _writeBody = _handle_text
+
+    def _handle_multipart(self, msg):
+        # The trick here is to write out each part separately, merge them all
+        # together, and then make sure that the boundary we've chosen isn't
+        # present in the payload.
+        msgtexts = []
+        subparts = msg.get_payload()
+        if subparts is None:
+            subparts = []
+        elif isinstance(subparts, str):
+            # e.g. a non-strict parse of a message with no starting boundary.
+            self.write(subparts)
+            return
+        elif not isinstance(subparts, list):
+            # Scalar payload
+            subparts = [subparts]
+        for part in subparts:
+            s = self._new_buffer()
+            g = self.clone(s)
+            g.flatten(part, unixfrom=False, linesep=self._NL)
+            msgtexts.append(s.getvalue())
+        # BAW: What about boundaries that are wrapped in double-quotes?
+        boundary = msg.get_boundary()
+        if not boundary:
+            # Create a boundary that doesn't appear in any of the
+            # message texts.
+            alltext = self._encoded_NL.join(msgtexts)
+            boundary = self._make_boundary(alltext)
+            msg.set_boundary(boundary)
+        # If there's a preamble, write it out, with a trailing CRLF
+        if msg.preamble is not None:
+            if self._mangle_from_:
+                preamble = fcre.sub('>From ', msg.preamble)
+            else:
+                preamble = msg.preamble
+            self._write_lines(preamble)
+            self.write(self._NL)
+        # dash-boundary transport-padding CRLF
+        self.write('--' + boundary + self._NL)
+        # body-part
+        if msgtexts:
+            self._fp.write(msgtexts.pop(0))
+        # *encapsulation
+        # --> delimiter transport-padding
+        # --> CRLF body-part
+        for body_part in msgtexts:
+            # delimiter transport-padding CRLF
+            self.write(self._NL + '--' + boundary + self._NL)
+            # body-part
+            self._fp.write(body_part)
+        # close-delimiter transport-padding
+        self.write(self._NL + '--' + boundary + '--' + self._NL)
+        if msg.epilogue is not None:
+            if self._mangle_from_:
+                epilogue = fcre.sub('>From ', msg.epilogue)
+            else:
+                epilogue = msg.epilogue
+            self._write_lines(epilogue)
+
+    def _handle_multipart_signed(self, msg):
+        # The contents of signed parts has to stay unmodified in order to keep
+        # the signature intact per RFC1847 2.1, so we disable header wrapping.
+        # RDM: This isn't enough to completely preserve the part, but it helps.
+        p = self.policy
+        self.policy = p.clone(max_line_length=0)
+        try:
+            self._handle_multipart(msg)
+        finally:
+            self.policy = p
+
+    def _handle_message_delivery_status(self, msg):
+        # We can't just write the headers directly to self's file object
+        # because this will leave an extra newline between the last header
+        # block and the boundary.  Sigh.
+        blocks = []
+        for part in msg.get_payload():
+            s = self._new_buffer()
+            g = self.clone(s)
+            g.flatten(part, unixfrom=False, linesep=self._NL)
+            text = s.getvalue()
+            lines = text.split(self._encoded_NL)
+            # Strip off the unnecessary trailing empty line
+            if lines and lines[-1] == self._encoded_EMPTY:
+                blocks.append(self._encoded_NL.join(lines[:-1]))
+            else:
+                blocks.append(text)
+        # Now join all the blocks with an empty line.  This has the lovely
+        # effect of separating each block with an empty line, but not adding
+        # an extra one after the last one.
+        self._fp.write(self._encoded_NL.join(blocks))
+
+    def _handle_message(self, msg):
+        s = self._new_buffer()
+        g = self.clone(s)
+        # The payload of a message/rfc822 part should be a multipart sequence
+        # of length 1.  The zeroth element of the list should be the Message
+        # object for the subpart.  Extract that object, stringify it, and
+        # write it out.
+        # Except, it turns out, when it's a string instead, which happens when
+        # and only when HeaderParser is used on a message of mime type
+        # message/rfc822.  Such messages are generated by, for example,
+        # Groupwise when forwarding unadorned messages.  (Issue 7970.)  So
+        # in that case we just emit the string body.
+        payload = msg._payload
+        if isinstance(payload, list):
+            g.flatten(msg.get_payload(0), unixfrom=False, linesep=self._NL)
+            payload = s.getvalue()
+        else:
+            payload = self._encode(payload)
+        self._fp.write(payload)
+
+    # This used to be a module level function; we use a classmethod for this
+    # and _compile_re so we can continue to provide the module level function
+    # for backward compatibility by doing
+    #   _make_boundary = Generator._make_boundary
+    # at the end of the module.  It *is* internal, so we could drop that...
+    @classmethod
+    def _make_boundary(cls, text=None):
+        # Craft a random boundary.  If text is given, ensure that the chosen
+        # boundary doesn't appear in the text.
+        token = random.randrange(sys.maxsize)
+        boundary = ('=' * 15) + (_fmt % token) + '=='
+        if text is None:
+            return boundary
+        b = boundary
+        counter = 0
+        while True:
+            cre = cls._compile_re('^--' + re.escape(b) + '(--)?$', re.MULTILINE)
+            if not cre.search(text):
+                break
+            b = boundary + '.' + str(counter)
+            counter += 1
+        return b
+
+    @classmethod
+    def _compile_re(cls, s, flags):
+        return re.compile(s, flags)
+
+
+class BytesGenerator(Generator):
+    """Generates a bytes version of a Message object tree.
+
+    Functionally identical to the base Generator except that the output is
+    bytes and not string.  When surrogates were used in the input to encode
+    bytes, these are decoded back to bytes for output.  If the policy has
+    cte_type set to 7bit, then the message is transformed such that the
+    non-ASCII bytes are properly content transfer encoded, using the charset
+    unknown-8bit.
+
+    The outfp object must accept bytes in its write method.
+    """
+
+    def write(self, s):
+        self._fp.write(s.encode('ascii', 'surrogateescape'))
+
+    def _new_buffer(self):
+        return BytesIO()
+
+    def _encode(self, s):
+        return s.encode('ascii')
+
+    def _write_headers(self, msg):
+        # This is almost the same as the string version, except for handling
+        # strings with 8bit bytes.
+        for h, v in msg.raw_items():
+            self._fp.write(self.policy.fold_binary(h, v))
+        # A blank line always separates headers from body
+        self.write(self._NL)
+
+    def _handle_text(self, msg):
+        # If the string has surrogates the original source was bytes, so
+        # just write it back out.
+        if msg._payload is None:
+            return
+        if _has_surrogates(msg._payload) and not self.policy.cte_type=='7bit':
+            if self._mangle_from_:
+                msg._payload = fcre.sub(">From ", msg._payload)
+            self._write_lines(msg._payload)
+        else:
+            super(BytesGenerator,self)._handle_text(msg)
+
+    # Default body handler
+    _writeBody = _handle_text
+
+    @classmethod
+    def _compile_re(cls, s, flags):
+        return re.compile(s.encode('ascii'), flags)
+
+
+
+_FMT = '[Non-text (%(type)s) part of message omitted, filename %(filename)s]'
+
+class DecodedGenerator(Generator):
+    """Generates a text representation of a message.
+
+    Like the Generator base class, except that non-text parts are substituted
+    with a format string representing the part.
+    """
+    def __init__(self, outfp, mangle_from_=None, maxheaderlen=None, fmt=None, *,
+                 policy=None):
+        """Like Generator.__init__() except that an additional optional
+        argument is allowed.
+
+        Walks through all subparts of a message.  If the subpart is of main
+        type `text', then it prints the decoded payload of the subpart.
+
+        Otherwise, fmt is a format string that is used instead of the message
+        payload.  fmt is expanded with the following keywords (in
+        %(keyword)s format):
+
+        type       : Full MIME type of the non-text part
+        maintype   : Main MIME type of the non-text part
+        subtype    : Sub-MIME type of the non-text part
+        filename   : Filename of the non-text part
+        description: Description associated with the non-text part
+        encoding   : Content transfer encoding of the non-text part
+
+        The default value for fmt is None, meaning
+
+        [Non-text (%(type)s) part of message omitted, filename %(filename)s]
+        """
+        Generator.__init__(self, outfp, mangle_from_, maxheaderlen,
+                           policy=policy)
+        if fmt is None:
+            self._fmt = _FMT
+        else:
+            self._fmt = fmt
+
+    def _dispatch(self, msg):
+        for part in msg.walk():
+            maintype = part.get_content_maintype()
+            if maintype == 'text':
+                print(part.get_payload(decode=False), file=self)
+            elif maintype == 'multipart':
+                # Just skip this
+                pass
+            else:
+                print(self._fmt % {
+                    'type'       : part.get_content_type(),
+                    'maintype'   : part.get_content_maintype(),
+                    'subtype'    : part.get_content_subtype(),
+                    'filename'   : part.get_filename('[no filename]'),
+                    'description': part.get('Content-Description',
+                                            '[no description]'),
+                    'encoding'   : part.get('Content-Transfer-Encoding',
+                                            '[no encoding]'),
+                    }, file=self)
+
+
+
+# Helper used by Generator._make_boundary
+_width = len(repr(sys.maxsize-1))
+_fmt = '%%0%dd' % _width
+
+# Backward compatibility
+_make_boundary = Generator._make_boundary
diff --git a/contrib/tools/python3/src/Lib/email/header.py b/contrib/tools/python3/src/Lib/email/header.py
new file mode 100644
index 0000000000..4ab0032bc6
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/header.py
@@ -0,0 +1,578 @@
+# Copyright (C) 2002-2007 Python Software Foundation
+# Author: Ben Gertzfield, Barry Warsaw
+# Contact: email-sig@python.org
+
+"""Header encoding and decoding functionality."""
+
+__all__ = [
+    'Header',
+    'decode_header',
+    'make_header',
+    ]
+
+import re
+import binascii
+
+import email.quoprimime
+import email.base64mime
+
+from email.errors import HeaderParseError
+from email import charset as _charset
+Charset = _charset.Charset
+
+NL = '\n'
+SPACE = ' '
+BSPACE = b' '
+SPACE8 = ' ' * 8
+EMPTYSTRING = ''
+MAXLINELEN = 78
+FWS = ' \t'
+
+USASCII = Charset('us-ascii')
+UTF8 = Charset('utf-8')
+
+# Match encoded-word strings in the form =?charset?q?Hello_World?=
+ecre = re.compile(r'''
+  =\?                   # literal =?
+  (?P<charset>[^?]*?)   # non-greedy up to the next ? is the charset
+  \?                    # literal ?
+  (?P<encoding>[qQbB])  # either a "q" or a "b", case insensitive
+  \?                    # literal ?
+  (?P<encoded>.*?)      # non-greedy up to the next ?= is the encoded string
+  \?=                   # literal ?=
+  ''', re.VERBOSE | re.MULTILINE)
+
+# Field name regexp, including trailing colon, but not separating whitespace,
+# according to RFC 2822.  Character range is from tilde to exclamation mark.
+# For use with .match()
+fcre = re.compile(r'[\041-\176]+:$')
+
+# Find a header embedded in a putative header value.  Used to check for
+# header injection attack.
+_embedded_header = re.compile(r'\n[^ \t]+:')
+
+
+
+# Helpers
+_max_append = email.quoprimime._max_append
+
+
+
+def decode_header(header):
+    """Decode a message header value without converting charset.
+
+    Returns a list of (string, charset) pairs containing each of the decoded
+    parts of the header.  Charset is None for non-encoded parts of the header,
+    otherwise a lower-case string containing the name of the character set
+    specified in the encoded string.
+
+    header may be a string that may or may not contain RFC2047 encoded words,
+    or it may be a Header object.
+
+    An email.errors.HeaderParseError may be raised when certain decoding error
+    occurs (e.g. a base64 decoding exception).
+    """
+    # If it is a Header object, we can just return the encoded chunks.
+    if hasattr(header, '_chunks'):
+        return [(_charset._encode(string, str(charset)), str(charset))
+                    for string, charset in header._chunks]
+    # If no encoding, just return the header with no charset.
+    if not ecre.search(header):
+        return [(header, None)]
+    # First step is to parse all the encoded parts into triplets of the form
+    # (encoded_string, encoding, charset).  For unencoded strings, the last
+    # two parts will be None.
+    words = []
+    for line in header.splitlines():
+        parts = ecre.split(line)
+        first = True
+        while parts:
+            unencoded = parts.pop(0)
+            if first:
+                unencoded = unencoded.lstrip()
+                first = False
+            if unencoded:
+                words.append((unencoded, None, None))
+            if parts:
+                charset = parts.pop(0).lower()
+                encoding = parts.pop(0).lower()
+                encoded = parts.pop(0)
+                words.append((encoded, encoding, charset))
+    # Now loop over words and remove words that consist of whitespace
+    # between two encoded strings.
+    droplist = []
+    for n, w in enumerate(words):
+        if n>1 and w[1] and words[n-2][1] and words[n-1][0].isspace():
+            droplist.append(n-1)
+    for d in reversed(droplist):
+        del words[d]
+
+    # The next step is to decode each encoded word by applying the reverse
+    # base64 or quopri transformation.  decoded_words is now a list of the
+    # form (decoded_word, charset).
+    decoded_words = []
+    for encoded_string, encoding, charset in words:
+        if encoding is None:
+            # This is an unencoded word.
+            decoded_words.append((encoded_string, charset))
+        elif encoding == 'q':
+            word = email.quoprimime.header_decode(encoded_string)
+            decoded_words.append((word, charset))
+        elif encoding == 'b':
+            paderr = len(encoded_string) % 4   # Postel's law: add missing padding
+            if paderr:
+                encoded_string += '==='[:4 - paderr]
+            try:
+                word = email.base64mime.decode(encoded_string)
+            except binascii.Error:
+                raise HeaderParseError('Base64 decoding error')
+            else:
+                decoded_words.append((word, charset))
+        else:
+            raise AssertionError('Unexpected encoding: ' + encoding)
+    # Now convert all words to bytes and collapse consecutive runs of
+    # similarly encoded words.
+    collapsed = []
+    last_word = last_charset = None
+    for word, charset in decoded_words:
+        if isinstance(word, str):
+            word = bytes(word, 'raw-unicode-escape')
+        if last_word is None:
+            last_word = word
+            last_charset = charset
+        elif charset != last_charset:
+            collapsed.append((last_word, last_charset))
+            last_word = word
+            last_charset = charset
+        elif last_charset is None:
+            last_word += BSPACE + word
+        else:
+            last_word += word
+    collapsed.append((last_word, last_charset))
+    return collapsed
+
+
+
+def make_header(decoded_seq, maxlinelen=None, header_name=None,
+                continuation_ws=' '):
+    """Create a Header from a sequence of pairs as returned by decode_header()
+
+    decode_header() takes a header value string and returns a sequence of
+    pairs of the format (decoded_string, charset) where charset is the string
+    name of the character set.
+
+    This function takes one of those sequence of pairs and returns a Header
+    instance.  Optional maxlinelen, header_name, and continuation_ws are as in
+    the Header constructor.
+    """
+    h = Header(maxlinelen=maxlinelen, header_name=header_name,
+               continuation_ws=continuation_ws)
+    for s, charset in decoded_seq:
+        # None means us-ascii but we can simply pass it on to h.append()
+        if charset is not None and not isinstance(charset, Charset):
+            charset = Charset(charset)
+        h.append(s, charset)
+    return h
+
+
+
+class Header:
+    def __init__(self, s=None, charset=None,
+                 maxlinelen=None, header_name=None,
+                 continuation_ws=' ', errors='strict'):
+        """Create a MIME-compliant header that can contain many character sets.
+
+        Optional s is the initial header value.  If None, the initial header
+        value is not set.  You can later append to the header with .append()
+        method calls.  s may be a byte string or a Unicode string, but see the
+        .append() documentation for semantics.
+
+        Optional charset serves two purposes: it has the same meaning as the
+        charset argument to the .append() method.  It also sets the default
+        character set for all subsequent .append() calls that omit the charset
+        argument.  If charset is not provided in the constructor, the us-ascii
+        charset is used both as s's initial charset and as the default for
+        subsequent .append() calls.
+
+        The maximum line length can be specified explicitly via maxlinelen. For
+        splitting the first line to a shorter value (to account for the field
+        header which isn't included in s, e.g. `Subject') pass in the name of
+        the field in header_name.  The default maxlinelen is 78 as recommended
+        by RFC 2822.
+
+        continuation_ws must be RFC 2822 compliant folding whitespace (usually
+        either a space or a hard tab) which will be prepended to continuation
+        lines.
+
+        errors is passed through to the .append() call.
+        """
+        if charset is None:
+            charset = USASCII
+        elif not isinstance(charset, Charset):
+            charset = Charset(charset)
+        self._charset = charset
+        self._continuation_ws = continuation_ws
+        self._chunks = []
+        if s is not None:
+            self.append(s, charset, errors)
+        if maxlinelen is None:
+            maxlinelen = MAXLINELEN
+        self._maxlinelen = maxlinelen
+        if header_name is None:
+            self._headerlen = 0
+        else:
+            # Take the separating colon and space into account.
+            self._headerlen = len(header_name) + 2
+
+    def __str__(self):
+        """Return the string value of the header."""
+        self._normalize()
+        uchunks = []
+        lastcs = None
+        lastspace = None
+        for string, charset in self._chunks:
+            # We must preserve spaces between encoded and non-encoded word
+            # boundaries, which means for us we need to add a space when we go
+            # from a charset to None/us-ascii, or from None/us-ascii to a
+            # charset.  Only do this for the second and subsequent chunks.
+            # Don't add a space if the None/us-ascii string already has
+            # a space (trailing or leading depending on transition)
+            nextcs = charset
+            if nextcs == _charset.UNKNOWN8BIT:
+                original_bytes = string.encode('ascii', 'surrogateescape')
+                string = original_bytes.decode('ascii', 'replace')
+            if uchunks:
+                hasspace = string and self._nonctext(string[0])
+                if lastcs not in (None, 'us-ascii'):
+                    if nextcs in (None, 'us-ascii') and not hasspace:
+                        uchunks.append(SPACE)
+                        nextcs = None
+                elif nextcs not in (None, 'us-ascii') and not lastspace:
+                    uchunks.append(SPACE)
+            lastspace = string and self._nonctext(string[-1])
+            lastcs = nextcs
+            uchunks.append(string)
+        return EMPTYSTRING.join(uchunks)
+
+    # Rich comparison operators for equality only.  BAW: does it make sense to
+    # have or explicitly disable <, <=, >, >= operators?
+    def __eq__(self, other):
+        # other may be a Header or a string.  Both are fine so coerce
+        # ourselves to a unicode (of the unencoded header value), swap the
+        # args and do another comparison.
+        return other == str(self)
+
+    def append(self, s, charset=None, errors='strict'):
+        """Append a string to the MIME header.
+
+        Optional charset, if given, should be a Charset instance or the name
+        of a character set (which will be converted to a Charset instance).  A
+        value of None (the default) means that the charset given in the
+        constructor is used.
+
+        s may be a byte string or a Unicode string.  If it is a byte string
+        (i.e. isinstance(s, str) is false), then charset is the encoding of
+        that byte string, and a UnicodeError will be raised if the string
+        cannot be decoded with that charset.  If s is a Unicode string, then
+        charset is a hint specifying the character set of the characters in
+        the string.  In either case, when producing an RFC 2822 compliant
+        header using RFC 2047 rules, the string will be encoded using the
+        output codec of the charset.  If the string cannot be encoded to the
+        output codec, a UnicodeError will be raised.
+
+        Optional `errors' is passed as the errors argument to the decode
+        call if s is a byte string.
+        """
+        if charset is None:
+            charset = self._charset
+        elif not isinstance(charset, Charset):
+            charset = Charset(charset)
+        if not isinstance(s, str):
+            input_charset = charset.input_codec or 'us-ascii'
+            if input_charset == _charset.UNKNOWN8BIT:
+                s = s.decode('us-ascii', 'surrogateescape')
+            else:
+                s = s.decode(input_charset, errors)
+        # Ensure that the bytes we're storing can be decoded to the output
+        # character set, otherwise an early error is raised.
+        output_charset = charset.output_codec or 'us-ascii'
+        if output_charset != _charset.UNKNOWN8BIT:
+            try:
+                s.encode(output_charset, errors)
+            except UnicodeEncodeError:
+                if output_charset!='us-ascii':
+                    raise
+                charset = UTF8
+        self._chunks.append((s, charset))
+
+    def _nonctext(self, s):
+        """True if string s is not a ctext character of RFC822.
+        """
+        return s.isspace() or s in ('(', ')', '\\')
+
+    def encode(self, splitchars=';, \t', maxlinelen=None, linesep='\n'):
+        r"""Encode a message header into an RFC-compliant format.
+
+        There are many issues involved in converting a given string for use in
+        an email header.  Only certain character sets are readable in most
+        email clients, and as header strings can only contain a subset of
+        7-bit ASCII, care must be taken to properly convert and encode (with
+        Base64 or quoted-printable) header strings.  In addition, there is a
+        75-character length limit on any given encoded header field, so
+        line-wrapping must be performed, even with double-byte character sets.
+
+        Optional maxlinelen specifies the maximum length of each generated
+        line, exclusive of the linesep string.  Individual lines may be longer
+        than maxlinelen if a folding point cannot be found.  The first line
+        will be shorter by the length of the header name plus ": " if a header
+        name was specified at Header construction time.  The default value for
+        maxlinelen is determined at header construction time.
+
+        Optional splitchars is a string containing characters which should be
+        given extra weight by the splitting algorithm during normal header
+        wrapping.  This is in very rough support of RFC 2822's `higher level
+        syntactic breaks':  split points preceded by a splitchar are preferred
+        during line splitting, with the characters preferred in the order in
+        which they appear in the string.  Space and tab may be included in the
+        string to indicate whether preference should be given to one over the
+        other as a split point when other split chars do not appear in the line
+        being split.  Splitchars does not affect RFC 2047 encoded lines.
+
+        Optional linesep is a string to be used to separate the lines of
+        the value.  The default value is the most useful for typical
+        Python applications, but it can be set to \r\n to produce RFC-compliant
+        line separators when needed.
+        """
+        self._normalize()
+        if maxlinelen is None:
+            maxlinelen = self._maxlinelen
+        # A maxlinelen of 0 means don't wrap.  For all practical purposes,
+        # choosing a huge number here accomplishes that and makes the
+        # _ValueFormatter algorithm much simpler.
+        if maxlinelen == 0:
+            maxlinelen = 1000000
+        formatter = _ValueFormatter(self._headerlen, maxlinelen,
+                                    self._continuation_ws, splitchars)
+        lastcs = None
+        hasspace = lastspace = None
+        for string, charset in self._chunks:
+            if hasspace is not None:
+                hasspace = string and self._nonctext(string[0])
+                if lastcs not in (None, 'us-ascii'):
+                    if not hasspace or charset not in (None, 'us-ascii'):
+                        formatter.add_transition()
+                elif charset not in (None, 'us-ascii') and not lastspace:
+                    formatter.add_transition()
+            lastspace = string and self._nonctext(string[-1])
+            lastcs = charset
+            hasspace = False
+            lines = string.splitlines()
+            if lines:
+                formatter.feed('', lines[0], charset)
+            else:
+                formatter.feed('', '', charset)
+            for line in lines[1:]:
+                formatter.newline()
+                if charset.header_encoding is not None:
+                    formatter.feed(self._continuation_ws, ' ' + line.lstrip(),
+                                   charset)
+                else:
+                    sline = line.lstrip()
+                    fws = line[:len(line)-len(sline)]
+                    formatter.feed(fws, sline, charset)
+            if len(lines) > 1:
+                formatter.newline()
+        if self._chunks:
+            formatter.add_transition()
+        value = formatter._str(linesep)
+        if _embedded_header.search(value):
+            raise HeaderParseError("header value appears to contain "
+                "an embedded header: {!r}".format(value))
+        return value
+
+    def _normalize(self):
+        # Step 1: Normalize the chunks so that all runs of identical charsets
+        # get collapsed into a single unicode string.
+        chunks = []
+        last_charset = None
+        last_chunk = []
+        for string, charset in self._chunks:
+            if charset == last_charset:
+                last_chunk.append(string)
+            else:
+                if last_charset is not None:
+                    chunks.append((SPACE.join(last_chunk), last_charset))
+                last_chunk = [string]
+                last_charset = charset
+        if last_chunk:
+            chunks.append((SPACE.join(last_chunk), last_charset))
+        self._chunks = chunks
+
+
+
+class _ValueFormatter:
+    def __init__(self, headerlen, maxlen, continuation_ws, splitchars):
+        self._maxlen = maxlen
+        self._continuation_ws = continuation_ws
+        self._continuation_ws_len = len(continuation_ws)
+        self._splitchars = splitchars
+        self._lines = []
+        self._current_line = _Accumulator(headerlen)
+
+    def _str(self, linesep):
+        self.newline()
+        return linesep.join(self._lines)
+
+    def __str__(self):
+        return self._str(NL)
+
+    def newline(self):
+        end_of_line = self._current_line.pop()
+        if end_of_line != (' ', ''):
+            self._current_line.push(*end_of_line)
+        if len(self._current_line) > 0:
+            if self._current_line.is_onlyws() and self._lines:
+                self._lines[-1] += str(self._current_line)
+            else:
+                self._lines.append(str(self._current_line))
+        self._current_line.reset()
+
+    def add_transition(self):
+        self._current_line.push(' ', '')
+
+    def feed(self, fws, string, charset):
+        # If the charset has no header encoding (i.e. it is an ASCII encoding)
+        # then we must split the header at the "highest level syntactic break"
+        # possible. Note that we don't have a lot of smarts about field
+        # syntax; we just try to break on semi-colons, then commas, then
+        # whitespace.  Eventually, this should be pluggable.
+        if charset.header_encoding is None:
+            self._ascii_split(fws, string, self._splitchars)
+            return
+        # Otherwise, we're doing either a Base64 or a quoted-printable
+        # encoding which means we don't need to split the line on syntactic
+        # breaks.  We can basically just find enough characters to fit on the
+        # current line, minus the RFC 2047 chrome.  What makes this trickier
+        # though is that we have to split at octet boundaries, not character
+        # boundaries but it's only safe to split at character boundaries so at
+        # best we can only get close.
+        encoded_lines = charset.header_encode_lines(string, self._maxlengths())
+        # The first element extends the current line, but if it's None then
+        # nothing more fit on the current line so start a new line.
+        try:
+            first_line = encoded_lines.pop(0)
+        except IndexError:
+            # There are no encoded lines, so we're done.
+            return
+        if first_line is not None:
+            self._append_chunk(fws, first_line)
+        try:
+            last_line = encoded_lines.pop()
+        except IndexError:
+            # There was only one line.
+            return
+        self.newline()
+        self._current_line.push(self._continuation_ws, last_line)
+        # Everything else are full lines in themselves.
+        for line in encoded_lines:
+            self._lines.append(self._continuation_ws + line)
+
+    def _maxlengths(self):
+        # The first line's length.
+        yield self._maxlen - len(self._current_line)
+        while True:
+            yield self._maxlen - self._continuation_ws_len
+
+    def _ascii_split(self, fws, string, splitchars):
+        # The RFC 2822 header folding algorithm is simple in principle but
+        # complex in practice.  Lines may be folded any place where "folding
+        # white space" appears by inserting a linesep character in front of the
+        # FWS.  The complication is that not all spaces or tabs qualify as FWS,
+        # and we are also supposed to prefer to break at "higher level
+        # syntactic breaks".  We can't do either of these without intimate
+        # knowledge of the structure of structured headers, which we don't have
+        # here.  So the best we can do here is prefer to break at the specified
+        # splitchars, and hope that we don't choose any spaces or tabs that
+        # aren't legal FWS.  (This is at least better than the old algorithm,
+        # where we would sometimes *introduce* FWS after a splitchar, or the
+        # algorithm before that, where we would turn all white space runs into
+        # single spaces or tabs.)
+        parts = re.split("(["+FWS+"]+)", fws+string)
+        if parts[0]:
+            parts[:0] = ['']
+        else:
+            parts.pop(0)
+        for fws, part in zip(*[iter(parts)]*2):
+            self._append_chunk(fws, part)
+
+    def _append_chunk(self, fws, string):
+        self._current_line.push(fws, string)
+        if len(self._current_line) > self._maxlen:
+            # Find the best split point, working backward from the end.
+            # There might be none, on a long first line.
+            for ch in self._splitchars:
+                for i in range(self._current_line.part_count()-1, 0, -1):
+                    if ch.isspace():
+                        fws = self._current_line[i][0]
+                        if fws and fws[0]==ch:
+                            break
+                    prevpart = self._current_line[i-1][1]
+                    if prevpart and prevpart[-1]==ch:
+                        break
+                else:
+                    continue
+                break
+            else:
+                fws, part = self._current_line.pop()
+                if self._current_line._initial_size > 0:
+                    # There will be a header, so leave it on a line by itself.
+                    self.newline()
+                    if not fws:
+                        # We don't use continuation_ws here because the whitespace
+                        # after a header should always be a space.
+                        fws = ' '
+                self._current_line.push(fws, part)
+                return
+            remainder = self._current_line.pop_from(i)
+            self._lines.append(str(self._current_line))
+            self._current_line.reset(remainder)
+
+
+class _Accumulator(list):
+
+    def __init__(self, initial_size=0):
+        self._initial_size = initial_size
+        super().__init__()
+
+    def push(self, fws, string):
+        self.append((fws, string))
+
+    def pop_from(self, i=0):
+        popped = self[i:]
+        self[i:] = []
+        return popped
+
+    def pop(self):
+        if self.part_count()==0:
+            return ('', '')
+        return super().pop()
+
+    def __len__(self):
+        return sum((len(fws)+len(part) for fws, part in self),
+                   self._initial_size)
+
+    def __str__(self):
+        return EMPTYSTRING.join((EMPTYSTRING.join((fws, part))
+                                for fws, part in self))
+
+    def reset(self, startval=None):
+        if startval is None:
+            startval = []
+        self[:] = startval
+        self._initial_size = 0
+
+    def is_onlyws(self):
+        return self._initial_size==0 and (not self or str(self).isspace())
+
+    def part_count(self):
+        return super().__len__()
diff --git a/contrib/tools/python3/src/Lib/email/headerregistry.py b/contrib/tools/python3/src/Lib/email/headerregistry.py
new file mode 100644
index 0000000000..5d84fc0d82
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/headerregistry.py
@@ -0,0 +1,601 @@
+"""Representing and manipulating email headers via custom objects.
+
+This module provides an implementation of the HeaderRegistry API.
+The implementation is designed to flexibly follow RFC5322 rules.
+
+Eventually HeaderRegistry will be a public API, but it isn't yet,
+and will probably change some before that happens.
+
+"""
+from types import MappingProxyType
+
+from email import utils
+from email import errors
+from email import _header_value_parser as parser
+
+class Address:
+
+    def __init__(self, display_name='', username='', domain='', addr_spec=None):
+        """Create an object representing a full email address.
+
+        An address can have a 'display_name', a 'username', and a 'domain'.  In
+        addition to specifying the username and domain separately, they may be
+        specified together by using the addr_spec keyword *instead of* the
+        username and domain keywords.  If an addr_spec string is specified it
+        must be properly quoted according to RFC 5322 rules; an error will be
+        raised if it is not.
+
+        An Address object has display_name, username, domain, and addr_spec
+        attributes, all of which are read-only.  The addr_spec and the string
+        value of the object are both quoted according to RFC5322 rules, but
+        without any Content Transfer Encoding.
+
+        """
+
+        inputs = ''.join(filter(None, (display_name, username, domain, addr_spec)))
+        if '\r' in inputs or '\n' in inputs:
+            raise ValueError("invalid arguments; address parts cannot contain CR or LF")
+
+        # This clause with its potential 'raise' may only happen when an
+        # application program creates an Address object using an addr_spec
+        # keyword.  The email library code itself must always supply username
+        # and domain.
+        if addr_spec is not None:
+            if username or domain:
+                raise TypeError("addrspec specified when username and/or "
+                                "domain also specified")
+            a_s, rest = parser.get_addr_spec(addr_spec)
+            if rest:
+                raise ValueError("Invalid addr_spec; only '{}' "
+                                 "could be parsed from '{}'".format(
+                                    a_s, addr_spec))
+            if a_s.all_defects:
+                raise a_s.all_defects[0]
+            username = a_s.local_part
+            domain = a_s.domain
+        self._display_name = display_name
+        self._username = username
+        self._domain = domain
+
+    @property
+    def display_name(self):
+        return self._display_name
+
+    @property
+    def username(self):
+        return self._username
+
+    @property
+    def domain(self):
+        return self._domain
+
+    @property
+    def addr_spec(self):
+        """The addr_spec (username@domain) portion of the address, quoted
+        according to RFC 5322 rules, but with no Content Transfer Encoding.
+        """
+        lp = self.username
+        if not parser.DOT_ATOM_ENDS.isdisjoint(lp):
+            lp = parser.quote_string(lp)
+        if self.domain:
+            return lp + '@' + self.domain
+        if not lp:
+            return '<>'
+        return lp
+
+    def __repr__(self):
+        return "{}(display_name={!r}, username={!r}, domain={!r})".format(
+                        self.__class__.__name__,
+                        self.display_name, self.username, self.domain)
+
+    def __str__(self):
+        disp = self.display_name
+        if not parser.SPECIALS.isdisjoint(disp):
+            disp = parser.quote_string(disp)
+        if disp:
+            addr_spec = '' if self.addr_spec=='<>' else self.addr_spec
+            return "{} <{}>".format(disp, addr_spec)
+        return self.addr_spec
+
+    def __eq__(self, other):
+        if not isinstance(other, Address):
+            return NotImplemented
+        return (self.display_name == other.display_name and
+                self.username == other.username and
+                self.domain == other.domain)
+
+
+class Group:
+
+    def __init__(self, display_name=None, addresses=None):
+        """Create an object representing an address group.
+
+        An address group consists of a display_name followed by colon and a
+        list of addresses (see Address) terminated by a semi-colon.  The Group
+        is created by specifying a display_name and a possibly empty list of
+        Address objects.  A Group can also be used to represent a single
+        address that is not in a group, which is convenient when manipulating
+        lists that are a combination of Groups and individual Addresses.  In
+        this case the display_name should be set to None.  In particular, the
+        string representation of a Group whose display_name is None is the same
+        as the Address object, if there is one and only one Address object in
+        the addresses list.
+
+        """
+        self._display_name = display_name
+        self._addresses = tuple(addresses) if addresses else tuple()
+
+    @property
+    def display_name(self):
+        return self._display_name
+
+    @property
+    def addresses(self):
+        return self._addresses
+
+    def __repr__(self):
+        return "{}(display_name={!r}, addresses={!r}".format(
+                 self.__class__.__name__,
+                 self.display_name, self.addresses)
+
+    def __str__(self):
+        if self.display_name is None and len(self.addresses)==1:
+            return str(self.addresses[0])
+        disp = self.display_name
+        if disp is not None and not parser.SPECIALS.isdisjoint(disp):
+            disp = parser.quote_string(disp)
+        adrstr = ", ".join(str(x) for x in self.addresses)
+        adrstr = ' ' + adrstr if adrstr else adrstr
+        return "{}:{};".format(disp, adrstr)
+
+    def __eq__(self, other):
+        if not isinstance(other, Group):
+            return NotImplemented
+        return (self.display_name == other.display_name and
+                self.addresses == other.addresses)
+
+
+# Header Classes #
+
+class BaseHeader(str):
+
+    """Base class for message headers.
+
+    Implements generic behavior and provides tools for subclasses.
+
+    A subclass must define a classmethod named 'parse' that takes an unfolded
+    value string and a dictionary as its arguments.  The dictionary will
+    contain one key, 'defects', initialized to an empty list.  After the call
+    the dictionary must contain two additional keys: parse_tree, set to the
+    parse tree obtained from parsing the header, and 'decoded', set to the
+    string value of the idealized representation of the data from the value.
+    (That is, encoded words are decoded, and values that have canonical
+    representations are so represented.)
+
+    The defects key is intended to collect parsing defects, which the message
+    parser will subsequently dispose of as appropriate.  The parser should not,
+    insofar as practical, raise any errors.  Defects should be added to the
+    list instead.  The standard header parsers register defects for RFC
+    compliance issues, for obsolete RFC syntax, and for unrecoverable parsing
+    errors.
+
+    The parse method may add additional keys to the dictionary.  In this case
+    the subclass must define an 'init' method, which will be passed the
+    dictionary as its keyword arguments.  The method should use (usually by
+    setting them as the value of similarly named attributes) and remove all the
+    extra keys added by its parse method, and then use super to call its parent
+    class with the remaining arguments and keywords.
+
+    The subclass should also make sure that a 'max_count' attribute is defined
+    that is either None or 1. XXX: need to better define this API.
+
+    """
+
+    def __new__(cls, name, value):
+        kwds = {'defects': []}
+        cls.parse(value, kwds)
+        if utils._has_surrogates(kwds['decoded']):
+            kwds['decoded'] = utils._sanitize(kwds['decoded'])
+        self = str.__new__(cls, kwds['decoded'])
+        del kwds['decoded']
+        self.init(name, **kwds)
+        return self
+
+    def init(self, name, *, parse_tree, defects):
+        self._name = name
+        self._parse_tree = parse_tree
+        self._defects = defects
+
+    @property
+    def name(self):
+        return self._name
+
+    @property
+    def defects(self):
+        return tuple(self._defects)
+
+    def __reduce__(self):
+        return (
+            _reconstruct_header,
+            (
+                self.__class__.__name__,
+                self.__class__.__bases__,
+                str(self),
+            ),
+            self.__dict__)
+
+    @classmethod
+    def _reconstruct(cls, value):
+        return str.__new__(cls, value)
+
+    def fold(self, *, policy):
+        """Fold header according to policy.
+
+        The parsed representation of the header is folded according to
+        RFC5322 rules, as modified by the policy.  If the parse tree
+        contains surrogateescaped bytes, the bytes are CTE encoded using
+        the charset 'unknown-8bit".
+
+        Any non-ASCII characters in the parse tree are CTE encoded using
+        charset utf-8. XXX: make this a policy setting.
+
+        The returned value is an ASCII-only string possibly containing linesep
+        characters, and ending with a linesep character.  The string includes
+        the header name and the ': ' separator.
+
+        """
+        # At some point we need to put fws here if it was in the source.
+        header = parser.Header([
+            parser.HeaderLabel([
+                parser.ValueTerminal(self.name, 'header-name'),
+                parser.ValueTerminal(':', 'header-sep')]),
+            ])
+        if self._parse_tree:
+            header.append(
+                parser.CFWSList([parser.WhiteSpaceTerminal(' ', 'fws')]))
+        header.append(self._parse_tree)
+        return header.fold(policy=policy)
+
+
+def _reconstruct_header(cls_name, bases, value):
+    return type(cls_name, bases, {})._reconstruct(value)
+
+
+class UnstructuredHeader:
+
+    max_count = None
+    value_parser = staticmethod(parser.get_unstructured)
+
+    @classmethod
+    def parse(cls, value, kwds):
+        kwds['parse_tree'] = cls.value_parser(value)
+        kwds['decoded'] = str(kwds['parse_tree'])
+
+
+class UniqueUnstructuredHeader(UnstructuredHeader):
+
+    max_count = 1
+
+
+class DateHeader:
+
+    """Header whose value consists of a single timestamp.
+
+    Provides an additional attribute, datetime, which is either an aware
+    datetime using a timezone, or a naive datetime if the timezone
+    in the input string is -0000.  Also accepts a datetime as input.
+    The 'value' attribute is the normalized form of the timestamp,
+    which means it is the output of format_datetime on the datetime.
+    """
+
+    max_count = None
+
+    # This is used only for folding, not for creating 'decoded'.
+    value_parser = staticmethod(parser.get_unstructured)
+
+    @classmethod
+    def parse(cls, value, kwds):
+        if not value:
+            kwds['defects'].append(errors.HeaderMissingRequiredValue())
+            kwds['datetime'] = None
+            kwds['decoded'] = ''
+            kwds['parse_tree'] = parser.TokenList()
+            return
+        if isinstance(value, str):
+            value = utils.parsedate_to_datetime(value)
+        kwds['datetime'] = value
+        kwds['decoded'] = utils.format_datetime(kwds['datetime'])
+        kwds['parse_tree'] = cls.value_parser(kwds['decoded'])
+
+    def init(self, *args, **kw):
+        self._datetime = kw.pop('datetime')
+        super().init(*args, **kw)
+
+    @property
+    def datetime(self):
+        return self._datetime
+
+
+class UniqueDateHeader(DateHeader):
+
+    max_count = 1
+
+
+class AddressHeader:
+
+    max_count = None
+
+    @staticmethod
+    def value_parser(value):
+        address_list, value = parser.get_address_list(value)
+        assert not value, 'this should not happen'
+        return address_list
+
+    @classmethod
+    def parse(cls, value, kwds):
+        if isinstance(value, str):
+            # We are translating here from the RFC language (address/mailbox)
+            # to our API language (group/address).
+            kwds['parse_tree'] = address_list = cls.value_parser(value)
+            groups = []
+            for addr in address_list.addresses:
+                groups.append(Group(addr.display_name,
+                                    [Address(mb.display_name or '',
+                                             mb.local_part or '',
+                                             mb.domain or '')
+                                     for mb in addr.all_mailboxes]))
+            defects = list(address_list.all_defects)
+        else:
+            # Assume it is Address/Group stuff
+            if not hasattr(value, '__iter__'):
+                value = [value]
+            groups = [Group(None, [item]) if not hasattr(item, 'addresses')
+                                          else item
+                                    for item in value]
+            defects = []
+        kwds['groups'] = groups
+        kwds['defects'] = defects
+        kwds['decoded'] = ', '.join([str(item) for item in groups])
+        if 'parse_tree' not in kwds:
+            kwds['parse_tree'] = cls.value_parser(kwds['decoded'])
+
+    def init(self, *args, **kw):
+        self._groups = tuple(kw.pop('groups'))
+        self._addresses = None
+        super().init(*args, **kw)
+
+    @property
+    def groups(self):
+        return self._groups
+
+    @property
+    def addresses(self):
+        if self._addresses is None:
+            self._addresses = tuple(address for group in self._groups
+                                            for address in group.addresses)
+        return self._addresses
+
+
+class UniqueAddressHeader(AddressHeader):
+
+    max_count = 1
+
+
+class SingleAddressHeader(AddressHeader):
+
+    @property
+    def address(self):
+        if len(self.addresses)!=1:
+            raise ValueError(("value of single address header {} is not "
+                "a single address").format(self.name))
+        return self.addresses[0]
+
+
+class UniqueSingleAddressHeader(SingleAddressHeader):
+
+    max_count = 1
+
+
+class MIMEVersionHeader:
+
+    max_count = 1
+
+    value_parser = staticmethod(parser.parse_mime_version)
+
+    @classmethod
+    def parse(cls, value, kwds):
+        kwds['parse_tree'] = parse_tree = cls.value_parser(value)
+        kwds['decoded'] = str(parse_tree)
+        kwds['defects'].extend(parse_tree.all_defects)
+        kwds['major'] = None if parse_tree.minor is None else parse_tree.major
+        kwds['minor'] = parse_tree.minor
+        if parse_tree.minor is not None:
+            kwds['version'] = '{}.{}'.format(kwds['major'], kwds['minor'])
+        else:
+            kwds['version'] = None
+
+    def init(self, *args, **kw):
+        self._version = kw.pop('version')
+        self._major = kw.pop('major')
+        self._minor = kw.pop('minor')
+        super().init(*args, **kw)
+
+    @property
+    def major(self):
+        return self._major
+
+    @property
+    def minor(self):
+        return self._minor
+
+    @property
+    def version(self):
+        return self._version
+
+
+class ParameterizedMIMEHeader:
+
+    # Mixin that handles the params dict.  Must be subclassed and
+    # a property value_parser for the specific header provided.
+
+    max_count = 1
+
+    @classmethod
+    def parse(cls, value, kwds):
+        kwds['parse_tree'] = parse_tree = cls.value_parser(value)
+        kwds['decoded'] = str(parse_tree)
+        kwds['defects'].extend(parse_tree.all_defects)
+        if parse_tree.params is None:
+            kwds['params'] = {}
+        else:
+            # The MIME RFCs specify that parameter ordering is arbitrary.
+            kwds['params'] = {utils._sanitize(name).lower():
+                                    utils._sanitize(value)
+                               for name, value in parse_tree.params}
+
+    def init(self, *args, **kw):
+        self._params = kw.pop('params')
+        super().init(*args, **kw)
+
+    @property
+    def params(self):
+        return MappingProxyType(self._params)
+
+
+class ContentTypeHeader(ParameterizedMIMEHeader):
+
+    value_parser = staticmethod(parser.parse_content_type_header)
+
+    def init(self, *args, **kw):
+        super().init(*args, **kw)
+        self._maintype = utils._sanitize(self._parse_tree.maintype)
+        self._subtype = utils._sanitize(self._parse_tree.subtype)
+
+    @property
+    def maintype(self):
+        return self._maintype
+
+    @property
+    def subtype(self):
+        return self._subtype
+
+    @property
+    def content_type(self):
+        return self.maintype + '/' + self.subtype
+
+
+class ContentDispositionHeader(ParameterizedMIMEHeader):
+
+    value_parser = staticmethod(parser.parse_content_disposition_header)
+
+    def init(self, *args, **kw):
+        super().init(*args, **kw)
+        cd = self._parse_tree.content_disposition
+        self._content_disposition = cd if cd is None else utils._sanitize(cd)
+
+    @property
+    def content_disposition(self):
+        return self._content_disposition
+
+
+class ContentTransferEncodingHeader:
+
+    max_count = 1
+
+    value_parser = staticmethod(parser.parse_content_transfer_encoding_header)
+
+    @classmethod
+    def parse(cls, value, kwds):
+        kwds['parse_tree'] = parse_tree = cls.value_parser(value)
+        kwds['decoded'] = str(parse_tree)
+        kwds['defects'].extend(parse_tree.all_defects)
+
+    def init(self, *args, **kw):
+        super().init(*args, **kw)
+        self._cte = utils._sanitize(self._parse_tree.cte)
+
+    @property
+    def cte(self):
+        return self._cte
+
+
+class MessageIDHeader:
+
+    max_count = 1
+    value_parser = staticmethod(parser.parse_message_id)
+
+    @classmethod
+    def parse(cls, value, kwds):
+        kwds['parse_tree'] = parse_tree = cls.value_parser(value)
+        kwds['decoded'] = str(parse_tree)
+        kwds['defects'].extend(parse_tree.all_defects)
+
+
+# The header factory #
+
+_default_header_map = {
+    'subject':                      UniqueUnstructuredHeader,
+    'date':                         UniqueDateHeader,
+    'resent-date':                  DateHeader,
+    'orig-date':                    UniqueDateHeader,
+    'sender':                       UniqueSingleAddressHeader,
+    'resent-sender':                SingleAddressHeader,
+    'to':                           UniqueAddressHeader,
+    'resent-to':                    AddressHeader,
+    'cc':                           UniqueAddressHeader,
+    'resent-cc':                    AddressHeader,
+    'bcc':                          UniqueAddressHeader,
+    'resent-bcc':                   AddressHeader,
+    'from':                         UniqueAddressHeader,
+    'resent-from':                  AddressHeader,
+    'reply-to':                     UniqueAddressHeader,
+    'mime-version':                 MIMEVersionHeader,
+    'content-type':                 ContentTypeHeader,
+    'content-disposition':          ContentDispositionHeader,
+    'content-transfer-encoding':    ContentTransferEncodingHeader,
+    'message-id':                   MessageIDHeader,
+    }
+
+class HeaderRegistry:
+
+    """A header_factory and header registry."""
+
+    def __init__(self, base_class=BaseHeader, default_class=UnstructuredHeader,
+                       use_default_map=True):
+        """Create a header_factory that works with the Policy API.
+
+        base_class is the class that will be the last class in the created
+        header class's __bases__ list.  default_class is the class that will be
+        used if "name" (see __call__) does not appear in the registry.
+        use_default_map controls whether or not the default mapping of names to
+        specialized classes is copied in to the registry when the factory is
+        created.  The default is True.
+
+        """
+        self.registry = {}
+        self.base_class = base_class
+        self.default_class = default_class
+        if use_default_map:
+            self.registry.update(_default_header_map)
+
+    def map_to_type(self, name, cls):
+        """Register cls as the specialized class for handling "name" headers.
+
+        """
+        self.registry[name.lower()] = cls
+
+    def __getitem__(self, name):
+        cls = self.registry.get(name.lower(), self.default_class)
+        return type('_'+cls.__name__, (cls, self.base_class), {})
+
+    def __call__(self, name, value):
+        """Create a header instance for header 'name' from 'value'.
+
+        Creates a header instance by creating a specialized class for parsing
+        and representing the specified header by combining the factory
+        base_class with a specialized class from the registry or the
+        default_class, and passing the name and value to the constructed
+        class's constructor.
+
+        """
+        return self[name](name, value)
diff --git a/contrib/tools/python3/src/Lib/email/iterators.py b/contrib/tools/python3/src/Lib/email/iterators.py
new file mode 100644
index 0000000000..b5502ee975
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/iterators.py
@@ -0,0 +1,71 @@
+# Copyright (C) 2001-2006 Python Software Foundation
+# Author: Barry Warsaw
+# Contact: email-sig@python.org
+
+"""Various types of useful iterators and generators."""
+
+__all__ = [
+    'body_line_iterator',
+    'typed_subpart_iterator',
+    'walk',
+    # Do not include _structure() since it's part of the debugging API.
+    ]
+
+import sys
+from io import StringIO
+
+
+
+# This function will become a method of the Message class
+def walk(self):
+    """Walk over the message tree, yielding each subpart.
+
+    The walk is performed in depth-first order.  This method is a
+    generator.
+    """
+    yield self
+    if self.is_multipart():
+        for subpart in self.get_payload():
+            yield from subpart.walk()
+
+
+
+# These two functions are imported into the Iterators.py interface module.
+def body_line_iterator(msg, decode=False):
+    """Iterate over the parts, returning string payloads line-by-line.
+
+    Optional decode (default False) is passed through to .get_payload().
+    """
+    for subpart in msg.walk():
+        payload = subpart.get_payload(decode=decode)
+        if isinstance(payload, str):
+            yield from StringIO(payload)
+
+
+def typed_subpart_iterator(msg, maintype='text', subtype=None):
+    """Iterate over the subparts with a given MIME type.
+
+    Use `maintype' as the main MIME type to match against; this defaults to
+    "text".  Optional `subtype' is the MIME subtype to match against; if
+    omitted, only the main type is matched.
+    """
+    for subpart in msg.walk():
+        if subpart.get_content_maintype() == maintype:
+            if subtype is None or subpart.get_content_subtype() == subtype:
+                yield subpart
+
+
+
+def _structure(msg, fp=None, level=0, include_default=False):
+    """A handy debugging aid"""
+    if fp is None:
+        fp = sys.stdout
+    tab = ' ' * (level * 4)
+    print(tab + msg.get_content_type(), end='', file=fp)
+    if include_default:
+        print(' [%s]' % msg.get_default_type(), file=fp)
+    else:
+        print(file=fp)
+    if msg.is_multipart():
+        for subpart in msg.get_payload():
+            _structure(subpart, fp, level+1, include_default)
diff --git a/contrib/tools/python3/src/Lib/email/message.py b/contrib/tools/python3/src/Lib/email/message.py
new file mode 100644
index 0000000000..6752ce0fa1
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/message.py
@@ -0,0 +1,1173 @@
+# Copyright (C) 2001-2007 Python Software Foundation
+# Author: Barry Warsaw
+# Contact: email-sig@python.org
+
+"""Basic message object for the email package object model."""
+
+__all__ = ['Message', 'EmailMessage']
+
+import re
+import uu
+import quopri
+from io import BytesIO, StringIO
+
+# Intrapackage imports
+from email import utils
+from email import errors
+from email._policybase import Policy, compat32
+from email import charset as _charset
+from email._encoded_words import decode_b
+Charset = _charset.Charset
+
+SEMISPACE = '; '
+
+# Regular expression that matches `special' characters in parameters, the
+# existence of which force quoting of the parameter value.
+tspecials = re.compile(r'[ \(\)<>@,;:\\"/\[\]\?=]')
+
+
+def _splitparam(param):
+    # Split header parameters.  BAW: this may be too simple.  It isn't
+    # strictly RFC 2045 (section 5.1) compliant, but it catches most headers
+    # found in the wild.  We may eventually need a full fledged parser.
+    # RDM: we might have a Header here; for now just stringify it.
+    a, sep, b = str(param).partition(';')
+    if not sep:
+        return a.strip(), None
+    return a.strip(), b.strip()
+
+def _formatparam(param, value=None, quote=True):
+    """Convenience function to format and return a key=value pair.
+
+    This will quote the value if needed or if quote is true.  If value is a
+    three tuple (charset, language, value), it will be encoded according
+    to RFC2231 rules.  If it contains non-ascii characters it will likewise
+    be encoded according to RFC2231 rules, using the utf-8 charset and
+    a null language.
+    """
+    if value is not None and len(value) > 0:
+        # A tuple is used for RFC 2231 encoded parameter values where items
+        # are (charset, language, value).  charset is a string, not a Charset
+        # instance.  RFC 2231 encoded values are never quoted, per RFC.
+        if isinstance(value, tuple):
+            # Encode as per RFC 2231
+            param += '*'
+            value = utils.encode_rfc2231(value[2], value[0], value[1])
+            return '%s=%s' % (param, value)
+        else:
+            try:
+                value.encode('ascii')
+            except UnicodeEncodeError:
+                param += '*'
+                value = utils.encode_rfc2231(value, 'utf-8', '')
+                return '%s=%s' % (param, value)
+        # BAW: Please check this.  I think that if quote is set it should
+        # force quoting even if not necessary.
+        if quote or tspecials.search(value):
+            return '%s="%s"' % (param, utils.quote(value))
+        else:
+            return '%s=%s' % (param, value)
+    else:
+        return param
+
+def _parseparam(s):
+    # RDM This might be a Header, so for now stringify it.
+    s = ';' + str(s)
+    plist = []
+    while s[:1] == ';':
+        s = s[1:]
+        end = s.find(';')
+        while end > 0 and (s.count('"', 0, end) - s.count('\\"', 0, end)) % 2:
+            end = s.find(';', end + 1)
+        if end < 0:
+            end = len(s)
+        f = s[:end]
+        if '=' in f:
+            i = f.index('=')
+            f = f[:i].strip().lower() + '=' + f[i+1:].strip()
+        plist.append(f.strip())
+        s = s[end:]
+    return plist
+
+
+def _unquotevalue(value):
+    # This is different than utils.collapse_rfc2231_value() because it doesn't
+    # try to convert the value to a unicode.  Message.get_param() and
+    # Message.get_params() are both currently defined to return the tuple in
+    # the face of RFC 2231 parameters.
+    if isinstance(value, tuple):
+        return value[0], value[1], utils.unquote(value[2])
+    else:
+        return utils.unquote(value)
+
+
+
+class Message:
+    """Basic message object.
+
+    A message object is defined as something that has a bunch of RFC 2822
+    headers and a payload.  It may optionally have an envelope header
+    (a.k.a. Unix-From or From_ header).  If the message is a container (i.e. a
+    multipart or a message/rfc822), then the payload is a list of Message
+    objects, otherwise it is a string.
+
+    Message objects implement part of the `mapping' interface, which assumes
+    there is exactly one occurrence of the header per message.  Some headers
+    do in fact appear multiple times (e.g. Received) and for those headers,
+    you must use the explicit API to set or get all the headers.  Not all of
+    the mapping methods are implemented.
+    """
+    def __init__(self, policy=compat32):
+        self.policy = policy
+        self._headers = []
+        self._unixfrom = None
+        self._payload = None
+        self._charset = None
+        # Defaults for multipart messages
+        self.preamble = self.epilogue = None
+        self.defects = []
+        # Default content type
+        self._default_type = 'text/plain'
+
+    def __str__(self):
+        """Return the entire formatted message as a string.
+        """
+        return self.as_string()
+
+    def as_string(self, unixfrom=False, maxheaderlen=0, policy=None):
+        """Return the entire formatted message as a string.
+
+        Optional 'unixfrom', when true, means include the Unix From_ envelope
+        header.  For backward compatibility reasons, if maxheaderlen is
+        not specified it defaults to 0, so you must override it explicitly
+        if you want a different maxheaderlen.  'policy' is passed to the
+        Generator instance used to serialize the message; if it is not
+        specified the policy associated with the message instance is used.
+
+        If the message object contains binary data that is not encoded
+        according to RFC standards, the non-compliant data will be replaced by
+        unicode "unknown character" code points.
+        """
+        from email.generator import Generator
+        policy = self.policy if policy is None else policy
+        fp = StringIO()
+        g = Generator(fp,
+                      mangle_from_=False,
+                      maxheaderlen=maxheaderlen,
+                      policy=policy)
+        g.flatten(self, unixfrom=unixfrom)
+        return fp.getvalue()
+
+    def __bytes__(self):
+        """Return the entire formatted message as a bytes object.
+        """
+        return self.as_bytes()
+
+    def as_bytes(self, unixfrom=False, policy=None):
+        """Return the entire formatted message as a bytes object.
+
+        Optional 'unixfrom', when true, means include the Unix From_ envelope
+        header.  'policy' is passed to the BytesGenerator instance used to
+        serialize the message; if not specified the policy associated with
+        the message instance is used.
+        """
+        from email.generator import BytesGenerator
+        policy = self.policy if policy is None else policy
+        fp = BytesIO()
+        g = BytesGenerator(fp, mangle_from_=False, policy=policy)
+        g.flatten(self, unixfrom=unixfrom)
+        return fp.getvalue()
+
+    def is_multipart(self):
+        """Return True if the message consists of multiple parts."""
+        return isinstance(self._payload, list)
+
+    #
+    # Unix From_ line
+    #
+    def set_unixfrom(self, unixfrom):
+        self._unixfrom = unixfrom
+
+    def get_unixfrom(self):
+        return self._unixfrom
+
+    #
+    # Payload manipulation.
+    #
+    def attach(self, payload):
+        """Add the given payload to the current payload.
+
+        The current payload will always be a list of objects after this method
+        is called.  If you want to set the payload to a scalar object, use
+        set_payload() instead.
+        """
+        if self._payload is None:
+            self._payload = [payload]
+        else:
+            try:
+                self._payload.append(payload)
+            except AttributeError:
+                raise TypeError("Attach is not valid on a message with a"
+                                " non-multipart payload")
+
+    def get_payload(self, i=None, decode=False):
+        """Return a reference to the payload.
+
+        The payload will either be a list object or a string.  If you mutate
+        the list object, you modify the message's payload in place.  Optional
+        i returns that index into the payload.
+
+        Optional decode is a flag indicating whether the payload should be
+        decoded or not, according to the Content-Transfer-Encoding header
+        (default is False).
+
+        When True and the message is not a multipart, the payload will be
+        decoded if this header's value is `quoted-printable' or `base64'.  If
+        some other encoding is used, or the header is missing, or if the
+        payload has bogus data (i.e. bogus base64 or uuencoded data), the
+        payload is returned as-is.
+
+        If the message is a multipart and the decode flag is True, then None
+        is returned.
+        """
+        # Here is the logic table for this code, based on the email5.0.0 code:
+        #   i     decode  is_multipart  result
+        # ------  ------  ------------  ------------------------------
+        #  None   True    True          None
+        #   i     True    True          None
+        #  None   False   True          _payload (a list)
+        #   i     False   True          _payload element i (a Message)
+        #   i     False   False         error (not a list)
+        #   i     True    False         error (not a list)
+        #  None   False   False         _payload
+        #  None   True    False         _payload decoded (bytes)
+        # Note that Barry planned to factor out the 'decode' case, but that
+        # isn't so easy now that we handle the 8 bit data, which needs to be
+        # converted in both the decode and non-decode path.
+        if self.is_multipart():
+            if decode:
+                return None
+            if i is None:
+                return self._payload
+            else:
+                return self._payload[i]
+        # For backward compatibility, Use isinstance and this error message
+        # instead of the more logical is_multipart test.
+        if i is not None and not isinstance(self._payload, list):
+            raise TypeError('Expected list, got %s' % type(self._payload))
+        payload = self._payload
+        # cte might be a Header, so for now stringify it.
+        cte = str(self.get('content-transfer-encoding', '')).lower()
+        # payload may be bytes here.
+        if isinstance(payload, str):
+            if utils._has_surrogates(payload):
+                bpayload = payload.encode('ascii', 'surrogateescape')
+                if not decode:
+                    try:
+                        payload = bpayload.decode(self.get_param('charset', 'ascii'), 'replace')
+                    except LookupError:
+                        payload = bpayload.decode('ascii', 'replace')
+            elif decode:
+                try:
+                    bpayload = payload.encode('ascii')
+                except UnicodeError:
+                    # This won't happen for RFC compliant messages (messages
+                    # containing only ASCII code points in the unicode input).
+                    # If it does happen, turn the string into bytes in a way
+                    # guaranteed not to fail.
+                    bpayload = payload.encode('raw-unicode-escape')
+        if not decode:
+            return payload
+        if cte == 'quoted-printable':
+            return quopri.decodestring(bpayload)
+        elif cte == 'base64':
+            # XXX: this is a bit of a hack; decode_b should probably be factored
+            # out somewhere, but I haven't figured out where yet.
+            value, defects = decode_b(b''.join(bpayload.splitlines()))
+            for defect in defects:
+                self.policy.handle_defect(self, defect)
+            return value
+        elif cte in ('x-uuencode', 'uuencode', 'uue', 'x-uue'):
+            in_file = BytesIO(bpayload)
+            out_file = BytesIO()
+            try:
+                uu.decode(in_file, out_file, quiet=True)
+                return out_file.getvalue()
+            except uu.Error:
+                # Some decoding problem
+                return bpayload
+        if isinstance(payload, str):
+            return bpayload
+        return payload
+
+    def set_payload(self, payload, charset=None):
+        """Set the payload to the given value.
+
+        Optional charset sets the message's default character set.  See
+        set_charset() for details.
+        """
+        if hasattr(payload, 'encode'):
+            if charset is None:
+                self._payload = payload
+                return
+            if not isinstance(charset, Charset):
+                charset = Charset(charset)
+            payload = payload.encode(charset.output_charset)
+        if hasattr(payload, 'decode'):
+            self._payload = payload.decode('ascii', 'surrogateescape')
+        else:
+            self._payload = payload
+        if charset is not None:
+            self.set_charset(charset)
+
+    def set_charset(self, charset):
+        """Set the charset of the payload to a given character set.
+
+        charset can be a Charset instance, a string naming a character set, or
+        None.  If it is a string it will be converted to a Charset instance.
+        If charset is None, the charset parameter will be removed from the
+        Content-Type field.  Anything else will generate a TypeError.
+
+        The message will be assumed to be of type text/* encoded with
+        charset.input_charset.  It will be converted to charset.output_charset
+        and encoded properly, if needed, when generating the plain text
+        representation of the message.  MIME headers (MIME-Version,
+        Content-Type, Content-Transfer-Encoding) will be added as needed.
+        """
+        if charset is None:
+            self.del_param('charset')
+            self._charset = None
+            return
+        if not isinstance(charset, Charset):
+            charset = Charset(charset)
+        self._charset = charset
+        if 'MIME-Version' not in self:
+            self.add_header('MIME-Version', '1.0')
+        if 'Content-Type' not in self:
+            self.add_header('Content-Type', 'text/plain',
+                            charset=charset.get_output_charset())
+        else:
+            self.set_param('charset', charset.get_output_charset())
+        if charset != charset.get_output_charset():
+            self._payload = charset.body_encode(self._payload)
+        if 'Content-Transfer-Encoding' not in self:
+            cte = charset.get_body_encoding()
+            try:
+                cte(self)
+            except TypeError:
+                # This 'if' is for backward compatibility, it allows unicode
+                # through even though that won't work correctly if the
+                # message is serialized.
+                payload = self._payload
+                if payload:
+                    try:
+                        payload = payload.encode('ascii', 'surrogateescape')
+                    except UnicodeError:
+                        payload = payload.encode(charset.output_charset)
+                self._payload = charset.body_encode(payload)
+                self.add_header('Content-Transfer-Encoding', cte)
+
+    def get_charset(self):
+        """Return the Charset instance associated with the message's payload.
+        """
+        return self._charset
+
+    #
+    # MAPPING INTERFACE (partial)
+    #
+    def __len__(self):
+        """Return the total number of headers, including duplicates."""
+        return len(self._headers)
+
+    def __getitem__(self, name):
+        """Get a header value.
+
+        Return None if the header is missing instead of raising an exception.
+
+        Note that if the header appeared multiple times, exactly which
+        occurrence gets returned is undefined.  Use get_all() to get all
+        the values matching a header field name.
+        """
+        return self.get(name)
+
+    def __setitem__(self, name, val):
+        """Set the value of a header.
+
+        Note: this does not overwrite an existing header with the same field
+        name.  Use __delitem__() first to delete any existing headers.
+        """
+        max_count = self.policy.header_max_count(name)
+        if max_count:
+            lname = name.lower()
+            found = 0
+            for k, v in self._headers:
+                if k.lower() == lname:
+                    found += 1
+                    if found >= max_count:
+                        raise ValueError("There may be at most {} {} headers "
+                                         "in a message".format(max_count, name))
+        self._headers.append(self.policy.header_store_parse(name, val))
+
+    def __delitem__(self, name):
+        """Delete all occurrences of a header, if present.
+
+        Does not raise an exception if the header is missing.
+        """
+        name = name.lower()
+        newheaders = []
+        for k, v in self._headers:
+            if k.lower() != name:
+                newheaders.append((k, v))
+        self._headers = newheaders
+
+    def __contains__(self, name):
+        return name.lower() in [k.lower() for k, v in self._headers]
+
+    def __iter__(self):
+        for field, value in self._headers:
+            yield field
+
+    def keys(self):
+        """Return a list of all the message's header field names.
+
+        These will be sorted in the order they appeared in the original
+        message, or were added to the message, and may contain duplicates.
+        Any fields deleted and re-inserted are always appended to the header
+        list.
+        """
+        return [k for k, v in self._headers]
+
+    def values(self):
+        """Return a list of all the message's header values.
+
+        These will be sorted in the order they appeared in the original
+        message, or were added to the message, and may contain duplicates.
+        Any fields deleted and re-inserted are always appended to the header
+        list.
+        """
+        return [self.policy.header_fetch_parse(k, v)
+                for k, v in self._headers]
+
+    def items(self):
+        """Get all the message's header fields and values.
+
+        These will be sorted in the order they appeared in the original
+        message, or were added to the message, and may contain duplicates.
+        Any fields deleted and re-inserted are always appended to the header
+        list.
+        """
+        return [(k, self.policy.header_fetch_parse(k, v))
+                for k, v in self._headers]
+
+    def get(self, name, failobj=None):
+        """Get a header value.
+
+        Like __getitem__() but return failobj instead of None when the field
+        is missing.
+        """
+        name = name.lower()
+        for k, v in self._headers:
+            if k.lower() == name:
+                return self.policy.header_fetch_parse(k, v)
+        return failobj
+
+    #
+    # "Internal" methods (public API, but only intended for use by a parser
+    # or generator, not normal application code.
+    #
+
+    def set_raw(self, name, value):
+        """Store name and value in the model without modification.
+
+        This is an "internal" API, intended only for use by a parser.
+        """
+        self._headers.append((name, value))
+
+    def raw_items(self):
+        """Return the (name, value) header pairs without modification.
+
+        This is an "internal" API, intended only for use by a generator.
+        """
+        return iter(self._headers.copy())
+
+    #
+    # Additional useful stuff
+    #
+
+    def get_all(self, name, failobj=None):
+        """Return a list of all the values for the named field.
+
+        These will be sorted in the order they appeared in the original
+        message, and may contain duplicates.  Any fields deleted and
+        re-inserted are always appended to the header list.
+
+        If no such fields exist, failobj is returned (defaults to None).
+        """
+        values = []
+        name = name.lower()
+        for k, v in self._headers:
+            if k.lower() == name:
+                values.append(self.policy.header_fetch_parse(k, v))
+        if not values:
+            return failobj
+        return values
+
+    def add_header(self, _name, _value, **_params):
+        """Extended header setting.
+
+        name is the header field to add.  keyword arguments can be used to set
+        additional parameters for the header field, with underscores converted
+        to dashes.  Normally the parameter will be added as key="value" unless
+        value is None, in which case only the key will be added.  If a
+        parameter value contains non-ASCII characters it can be specified as a
+        three-tuple of (charset, language, value), in which case it will be
+        encoded according to RFC2231 rules.  Otherwise it will be encoded using
+        the utf-8 charset and a language of ''.
+
+        Examples:
+
+        msg.add_header('content-disposition', 'attachment', filename='bud.gif')
+        msg.add_header('content-disposition', 'attachment',
+                       filename=('utf-8', '', Fußballer.ppt'))
+        msg.add_header('content-disposition', 'attachment',
+                       filename='Fußballer.ppt'))
+        """
+        parts = []
+        for k, v in _params.items():
+            if v is None:
+                parts.append(k.replace('_', '-'))
+            else:
+                parts.append(_formatparam(k.replace('_', '-'), v))
+        if _value is not None:
+            parts.insert(0, _value)
+        self[_name] = SEMISPACE.join(parts)
+
+    def replace_header(self, _name, _value):
+        """Replace a header.
+
+        Replace the first matching header found in the message, retaining
+        header order and case.  If no matching header was found, a KeyError is
+        raised.
+        """
+        _name = _name.lower()
+        for i, (k, v) in zip(range(len(self._headers)), self._headers):
+            if k.lower() == _name:
+                self._headers[i] = self.policy.header_store_parse(k, _value)
+                break
+        else:
+            raise KeyError(_name)
+
+    #
+    # Use these three methods instead of the three above.
+    #
+
+    def get_content_type(self):
+        """Return the message's content type.
+
+        The returned string is coerced to lower case of the form
+        `maintype/subtype'.  If there was no Content-Type header in the
+        message, the default type as given by get_default_type() will be
+        returned.  Since according to RFC 2045, messages always have a default
+        type this will always return a value.
+
+        RFC 2045 defines a message's default type to be text/plain unless it
+        appears inside a multipart/digest container, in which case it would be
+        message/rfc822.
+        """
+        missing = object()
+        value = self.get('content-type', missing)
+        if value is missing:
+            # This should have no parameters
+            return self.get_default_type()
+        ctype = _splitparam(value)[0].lower()
+        # RFC 2045, section 5.2 says if its invalid, use text/plain
+        if ctype.count('/') != 1:
+            return 'text/plain'
+        return ctype
+
+    def get_content_maintype(self):
+        """Return the message's main content type.
+
+        This is the `maintype' part of the string returned by
+        get_content_type().
+        """
+        ctype = self.get_content_type()
+        return ctype.split('/')[0]
+
+    def get_content_subtype(self):
+        """Returns the message's sub-content type.
+
+        This is the `subtype' part of the string returned by
+        get_content_type().
+        """
+        ctype = self.get_content_type()
+        return ctype.split('/')[1]
+
+    def get_default_type(self):
+        """Return the `default' content type.
+
+        Most messages have a default content type of text/plain, except for
+        messages that are subparts of multipart/digest containers.  Such
+        subparts have a default content type of message/rfc822.
+        """
+        return self._default_type
+
+    def set_default_type(self, ctype):
+        """Set the `default' content type.
+
+        ctype should be either "text/plain" or "message/rfc822", although this
+        is not enforced.  The default content type is not stored in the
+        Content-Type header.
+        """
+        self._default_type = ctype
+
+    def _get_params_preserve(self, failobj, header):
+        # Like get_params() but preserves the quoting of values.  BAW:
+        # should this be part of the public interface?
+        missing = object()
+        value = self.get(header, missing)
+        if value is missing:
+            return failobj
+        params = []
+        for p in _parseparam(value):
+            try:
+                name, val = p.split('=', 1)
+                name = name.strip()
+                val = val.strip()
+            except ValueError:
+                # Must have been a bare attribute
+                name = p.strip()
+                val = ''
+            params.append((name, val))
+        params = utils.decode_params(params)
+        return params
+
+    def get_params(self, failobj=None, header='content-type', unquote=True):
+        """Return the message's Content-Type parameters, as a list.
+
+        The elements of the returned list are 2-tuples of key/value pairs, as
+        split on the `=' sign.  The left hand side of the `=' is the key,
+        while the right hand side is the value.  If there is no `=' sign in
+        the parameter the value is the empty string.  The value is as
+        described in the get_param() method.
+
+        Optional failobj is the object to return if there is no Content-Type
+        header.  Optional header is the header to search instead of
+        Content-Type.  If unquote is True, the value is unquoted.
+        """
+        missing = object()
+        params = self._get_params_preserve(missing, header)
+        if params is missing:
+            return failobj
+        if unquote:
+            return [(k, _unquotevalue(v)) for k, v in params]
+        else:
+            return params
+
+    def get_param(self, param, failobj=None, header='content-type',
+                  unquote=True):
+        """Return the parameter value if found in the Content-Type header.
+
+        Optional failobj is the object to return if there is no Content-Type
+        header, or the Content-Type header has no such parameter.  Optional
+        header is the header to search instead of Content-Type.
+
+        Parameter keys are always compared case insensitively.  The return
+        value can either be a string, or a 3-tuple if the parameter was RFC
+        2231 encoded.  When it's a 3-tuple, the elements of the value are of
+        the form (CHARSET, LANGUAGE, VALUE).  Note that both CHARSET and
+        LANGUAGE can be None, in which case you should consider VALUE to be
+        encoded in the us-ascii charset.  You can usually ignore LANGUAGE.
+        The parameter value (either the returned string, or the VALUE item in
+        the 3-tuple) is always unquoted, unless unquote is set to False.
+
+        If your application doesn't care whether the parameter was RFC 2231
+        encoded, it can turn the return value into a string as follows:
+
+            rawparam = msg.get_param('foo')
+            param = email.utils.collapse_rfc2231_value(rawparam)
+
+        """
+        if header not in self:
+            return failobj
+        for k, v in self._get_params_preserve(failobj, header):
+            if k.lower() == param.lower():
+                if unquote:
+                    return _unquotevalue(v)
+                else:
+                    return v
+        return failobj
+
+    def set_param(self, param, value, header='Content-Type', requote=True,
+                  charset=None, language='', replace=False):
+        """Set a parameter in the Content-Type header.
+
+        If the parameter already exists in the header, its value will be
+        replaced with the new value.
+
+        If header is Content-Type and has not yet been defined for this
+        message, it will be set to "text/plain" and the new parameter and
+        value will be appended as per RFC 2045.
+
+        An alternate header can be specified in the header argument, and all
+        parameters will be quoted as necessary unless requote is False.
+
+        If charset is specified, the parameter will be encoded according to RFC
+        2231.  Optional language specifies the RFC 2231 language, defaulting
+        to the empty string.  Both charset and language should be strings.
+        """
+        if not isinstance(value, tuple) and charset:
+            value = (charset, language, value)
+
+        if header not in self and header.lower() == 'content-type':
+            ctype = 'text/plain'
+        else:
+            ctype = self.get(header)
+        if not self.get_param(param, header=header):
+            if not ctype:
+                ctype = _formatparam(param, value, requote)
+            else:
+                ctype = SEMISPACE.join(
+                    [ctype, _formatparam(param, value, requote)])
+        else:
+            ctype = ''
+            for old_param, old_value in self.get_params(header=header,
+                                                        unquote=requote):
+                append_param = ''
+                if old_param.lower() == param.lower():
+                    append_param = _formatparam(param, value, requote)
+                else:
+                    append_param = _formatparam(old_param, old_value, requote)
+                if not ctype:
+                    ctype = append_param
+                else:
+                    ctype = SEMISPACE.join([ctype, append_param])
+        if ctype != self.get(header):
+            if replace:
+                self.replace_header(header, ctype)
+            else:
+                del self[header]
+                self[header] = ctype
+
+    def del_param(self, param, header='content-type', requote=True):
+        """Remove the given parameter completely from the Content-Type header.
+
+        The header will be re-written in place without the parameter or its
+        value. All values will be quoted as necessary unless requote is
+        False.  Optional header specifies an alternative to the Content-Type
+        header.
+        """
+        if header not in self:
+            return
+        new_ctype = ''
+        for p, v in self.get_params(header=header, unquote=requote):
+            if p.lower() != param.lower():
+                if not new_ctype:
+                    new_ctype = _formatparam(p, v, requote)
+                else:
+                    new_ctype = SEMISPACE.join([new_ctype,
+                                                _formatparam(p, v, requote)])
+        if new_ctype != self.get(header):
+            del self[header]
+            self[header] = new_ctype
+
+    def set_type(self, type, header='Content-Type', requote=True):
+        """Set the main type and subtype for the Content-Type header.
+
+        type must be a string in the form "maintype/subtype", otherwise a
+        ValueError is raised.
+
+        This method replaces the Content-Type header, keeping all the
+        parameters in place.  If requote is False, this leaves the existing
+        header's quoting as is.  Otherwise, the parameters will be quoted (the
+        default).
+
+        An alternative header can be specified in the header argument.  When
+        the Content-Type header is set, we'll always also add a MIME-Version
+        header.
+        """
+        # BAW: should we be strict?
+        if not type.count('/') == 1:
+            raise ValueError
+        # Set the Content-Type, you get a MIME-Version
+        if header.lower() == 'content-type':
+            del self['mime-version']
+            self['MIME-Version'] = '1.0'
+        if header not in self:
+            self[header] = type
+            return
+        params = self.get_params(header=header, unquote=requote)
+        del self[header]
+        self[header] = type
+        # Skip the first param; it's the old type.
+        for p, v in params[1:]:
+            self.set_param(p, v, header, requote)
+
+    def get_filename(self, failobj=None):
+        """Return the filename associated with the payload if present.
+
+        The filename is extracted from the Content-Disposition header's
+        `filename' parameter, and it is unquoted.  If that header is missing
+        the `filename' parameter, this method falls back to looking for the
+        `name' parameter.
+        """
+        missing = object()
+        filename = self.get_param('filename', missing, 'content-disposition')
+        if filename is missing:
+            filename = self.get_param('name', missing, 'content-type')
+        if filename is missing:
+            return failobj
+        return utils.collapse_rfc2231_value(filename).strip()
+
+    def get_boundary(self, failobj=None):
+        """Return the boundary associated with the payload if present.
+
+        The boundary is extracted from the Content-Type header's `boundary'
+        parameter, and it is unquoted.
+        """
+        missing = object()
+        boundary = self.get_param('boundary', missing)
+        if boundary is missing:
+            return failobj
+        # RFC 2046 says that boundaries may begin but not end in w/s
+        return utils.collapse_rfc2231_value(boundary).rstrip()
+
+    def set_boundary(self, boundary):
+        """Set the boundary parameter in Content-Type to 'boundary'.
+
+        This is subtly different than deleting the Content-Type header and
+        adding a new one with a new boundary parameter via add_header().  The
+        main difference is that using the set_boundary() method preserves the
+        order of the Content-Type header in the original message.
+
+        HeaderParseError is raised if the message has no Content-Type header.
+        """
+        missing = object()
+        params = self._get_params_preserve(missing, 'content-type')
+        if params is missing:
+            # There was no Content-Type header, and we don't know what type
+            # to set it to, so raise an exception.
+            raise errors.HeaderParseError('No Content-Type header found')
+        newparams = []
+        foundp = False
+        for pk, pv in params:
+            if pk.lower() == 'boundary':
+                newparams.append(('boundary', '"%s"' % boundary))
+                foundp = True
+            else:
+                newparams.append((pk, pv))
+        if not foundp:
+            # The original Content-Type header had no boundary attribute.
+            # Tack one on the end.  BAW: should we raise an exception
+            # instead???
+            newparams.append(('boundary', '"%s"' % boundary))
+        # Replace the existing Content-Type header with the new value
+        newheaders = []
+        for h, v in self._headers:
+            if h.lower() == 'content-type':
+                parts = []
+                for k, v in newparams:
+                    if v == '':
+                        parts.append(k)
+                    else:
+                        parts.append('%s=%s' % (k, v))
+                val = SEMISPACE.join(parts)
+                newheaders.append(self.policy.header_store_parse(h, val))
+
+            else:
+                newheaders.append((h, v))
+        self._headers = newheaders
+
+    def get_content_charset(self, failobj=None):
+        """Return the charset parameter of the Content-Type header.
+
+        The returned string is always coerced to lower case.  If there is no
+        Content-Type header, or if that header has no charset parameter,
+        failobj is returned.
+        """
+        missing = object()
+        charset = self.get_param('charset', missing)
+        if charset is missing:
+            return failobj
+        if isinstance(charset, tuple):
+            # RFC 2231 encoded, so decode it, and it better end up as ascii.
+            pcharset = charset[0] or 'us-ascii'
+            try:
+                # LookupError will be raised if the charset isn't known to
+                # Python.  UnicodeError will be raised if the encoded text
+                # contains a character not in the charset.
+                as_bytes = charset[2].encode('raw-unicode-escape')
+                charset = str(as_bytes, pcharset)
+            except (LookupError, UnicodeError):
+                charset = charset[2]
+        # charset characters must be in us-ascii range
+        try:
+            charset.encode('us-ascii')
+        except UnicodeError:
+            return failobj
+        # RFC 2046, $4.1.2 says charsets are not case sensitive
+        return charset.lower()
+
+    def get_charsets(self, failobj=None):
+        """Return a list containing the charset(s) used in this message.
+
+        The returned list of items describes the Content-Type headers'
+        charset parameter for this message and all the subparts in its
+        payload.
+
+        Each item will either be a string (the value of the charset parameter
+        in the Content-Type header of that part) or the value of the
+        'failobj' parameter (defaults to None), if the part does not have a
+        main MIME type of "text", or the charset is not defined.
+
+        The list will contain one string for each part of the message, plus
+        one for the container message (i.e. self), so that a non-multipart
+        message will still return a list of length 1.
+        """
+        return [part.get_content_charset(failobj) for part in self.walk()]
+
+    def get_content_disposition(self):
+        """Return the message's content-disposition if it exists, or None.
+
+        The return values can be either 'inline', 'attachment' or None
+        according to the rfc2183.
+        """
+        value = self.get('content-disposition')
+        if value is None:
+            return None
+        c_d = _splitparam(value)[0].lower()
+        return c_d
+
+    # I.e. def walk(self): ...
+    from email.iterators import walk
+
+
+class MIMEPart(Message):
+
+    def __init__(self, policy=None):
+        if policy is None:
+            from email.policy import default
+            policy = default
+        super().__init__(policy)
+
+
+    def as_string(self, unixfrom=False, maxheaderlen=None, policy=None):
+        """Return the entire formatted message as a string.
+
+        Optional 'unixfrom', when true, means include the Unix From_ envelope
+        header.  maxheaderlen is retained for backward compatibility with the
+        base Message class, but defaults to None, meaning that the policy value
+        for max_line_length controls the header maximum length.  'policy' is
+        passed to the Generator instance used to serialize the message; if it
+        is not specified the policy associated with the message instance is
+        used.
+        """
+        policy = self.policy if policy is None else policy
+        if maxheaderlen is None:
+            maxheaderlen = policy.max_line_length
+        return super().as_string(unixfrom, maxheaderlen, policy)
+
+    def __str__(self):
+        return self.as_string(policy=self.policy.clone(utf8=True))
+
+    def is_attachment(self):
+        c_d = self.get('content-disposition')
+        return False if c_d is None else c_d.content_disposition == 'attachment'
+
+    def _find_body(self, part, preferencelist):
+        if part.is_attachment():
+            return
+        maintype, subtype = part.get_content_type().split('/')
+        if maintype == 'text':
+            if subtype in preferencelist:
+                yield (preferencelist.index(subtype), part)
+            return
+        if maintype != 'multipart' or not self.is_multipart():
+            return
+        if subtype != 'related':
+            for subpart in part.iter_parts():
+                yield from self._find_body(subpart, preferencelist)
+            return
+        if 'related' in preferencelist:
+            yield (preferencelist.index('related'), part)
+        candidate = None
+        start = part.get_param('start')
+        if start:
+            for subpart in part.iter_parts():
+                if subpart['content-id'] == start:
+                    candidate = subpart
+                    break
+        if candidate is None:
+            subparts = part.get_payload()
+            candidate = subparts[0] if subparts else None
+        if candidate is not None:
+            yield from self._find_body(candidate, preferencelist)
+
+    def get_body(self, preferencelist=('related', 'html', 'plain')):
+        """Return best candidate mime part for display as 'body' of message.
+
+        Do a depth first search, starting with self, looking for the first part
+        matching each of the items in preferencelist, and return the part
+        corresponding to the first item that has a match, or None if no items
+        have a match.  If 'related' is not included in preferencelist, consider
+        the root part of any multipart/related encountered as a candidate
+        match.  Ignore parts with 'Content-Disposition: attachment'.
+        """
+        best_prio = len(preferencelist)
+        body = None
+        for prio, part in self._find_body(self, preferencelist):
+            if prio < best_prio:
+                best_prio = prio
+                body = part
+                if prio == 0:
+                    break
+        return body
+
+    _body_types = {('text', 'plain'),
+                   ('text', 'html'),
+                   ('multipart', 'related'),
+                   ('multipart', 'alternative')}
+    def iter_attachments(self):
+        """Return an iterator over the non-main parts of a multipart.
+
+        Skip the first of each occurrence of text/plain, text/html,
+        multipart/related, or multipart/alternative in the multipart (unless
+        they have a 'Content-Disposition: attachment' header) and include all
+        remaining subparts in the returned iterator.  When applied to a
+        multipart/related, return all parts except the root part.  Return an
+        empty iterator when applied to a multipart/alternative or a
+        non-multipart.
+        """
+        maintype, subtype = self.get_content_type().split('/')
+        if maintype != 'multipart' or subtype == 'alternative':
+            return
+        payload = self.get_payload()
+        # Certain malformed messages can have content type set to `multipart/*`
+        # but still have single part body, in which case payload.copy() can
+        # fail with AttributeError.
+        try:
+            parts = payload.copy()
+        except AttributeError:
+            # payload is not a list, it is most probably a string.
+            return
+
+        if maintype == 'multipart' and subtype == 'related':
+            # For related, we treat everything but the root as an attachment.
+            # The root may be indicated by 'start'; if there's no start or we
+            # can't find the named start, treat the first subpart as the root.
+            start = self.get_param('start')
+            if start:
+                found = False
+                attachments = []
+                for part in parts:
+                    if part.get('content-id') == start:
+                        found = True
+                    else:
+                        attachments.append(part)
+                if found:
+                    yield from attachments
+                    return
+            parts.pop(0)
+            yield from parts
+            return
+        # Otherwise we more or less invert the remaining logic in get_body.
+        # This only really works in edge cases (ex: non-text related or
+        # alternatives) if the sending agent sets content-disposition.
+        seen = []   # Only skip the first example of each candidate type.
+        for part in parts:
+            maintype, subtype = part.get_content_type().split('/')
+            if ((maintype, subtype) in self._body_types and
+                    not part.is_attachment() and subtype not in seen):
+                seen.append(subtype)
+                continue
+            yield part
+
+    def iter_parts(self):
+        """Return an iterator over all immediate subparts of a multipart.
+
+        Return an empty iterator for a non-multipart.
+        """
+        if self.is_multipart():
+            yield from self.get_payload()
+
+    def get_content(self, *args, content_manager=None, **kw):
+        if content_manager is None:
+            content_manager = self.policy.content_manager
+        return content_manager.get_content(self, *args, **kw)
+
+    def set_content(self, *args, content_manager=None, **kw):
+        if content_manager is None:
+            content_manager = self.policy.content_manager
+        content_manager.set_content(self, *args, **kw)
+
+    def _make_multipart(self, subtype, disallowed_subtypes, boundary):
+        if self.get_content_maintype() == 'multipart':
+            existing_subtype = self.get_content_subtype()
+            disallowed_subtypes = disallowed_subtypes + (subtype,)
+            if existing_subtype in disallowed_subtypes:
+                raise ValueError("Cannot convert {} to {}".format(
+                    existing_subtype, subtype))
+        keep_headers = []
+        part_headers = []
+        for name, value in self._headers:
+            if name.lower().startswith('content-'):
+                part_headers.append((name, value))
+            else:
+                keep_headers.append((name, value))
+        if part_headers:
+            # There is existing content, move it to the first subpart.
+            part = type(self)(policy=self.policy)
+            part._headers = part_headers
+            part._payload = self._payload
+            self._payload = [part]
+        else:
+            self._payload = []
+        self._headers = keep_headers
+        self['Content-Type'] = 'multipart/' + subtype
+        if boundary is not None:
+            self.set_param('boundary', boundary)
+
+    def make_related(self, boundary=None):
+        self._make_multipart('related', ('alternative', 'mixed'), boundary)
+
+    def make_alternative(self, boundary=None):
+        self._make_multipart('alternative', ('mixed',), boundary)
+
+    def make_mixed(self, boundary=None):
+        self._make_multipart('mixed', (), boundary)
+
+    def _add_multipart(self, _subtype, *args, _disp=None, **kw):
+        if (self.get_content_maintype() != 'multipart' or
+                self.get_content_subtype() != _subtype):
+            getattr(self, 'make_' + _subtype)()
+        part = type(self)(policy=self.policy)
+        part.set_content(*args, **kw)
+        if _disp and 'content-disposition' not in part:
+            part['Content-Disposition'] = _disp
+        self.attach(part)
+
+    def add_related(self, *args, **kw):
+        self._add_multipart('related', *args, _disp='inline', **kw)
+
+    def add_alternative(self, *args, **kw):
+        self._add_multipart('alternative', *args, **kw)
+
+    def add_attachment(self, *args, **kw):
+        self._add_multipart('mixed', *args, _disp='attachment', **kw)
+
+    def clear(self):
+        self._headers = []
+        self._payload = None
+
+    def clear_content(self):
+        self._headers = [(n, v) for n, v in self._headers
+                         if not n.lower().startswith('content-')]
+        self._payload = None
+
+
+class EmailMessage(MIMEPart):
+
+    def set_content(self, *args, **kw):
+        super().set_content(*args, **kw)
+        if 'MIME-Version' not in self:
+            self['MIME-Version'] = '1.0'
diff --git a/contrib/tools/python3/src/Lib/email/mime/__init__.py b/contrib/tools/python3/src/Lib/email/mime/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/mime/__init__.py
diff --git a/contrib/tools/python3/src/Lib/email/mime/application.py b/contrib/tools/python3/src/Lib/email/mime/application.py
new file mode 100644
index 0000000000..6877e554e1
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/mime/application.py
@@ -0,0 +1,37 @@
+# Copyright (C) 2001-2006 Python Software Foundation
+# Author: Keith Dart
+# Contact: email-sig@python.org
+
+"""Class representing application/* type MIME documents."""
+
+__all__ = ["MIMEApplication"]
+
+from email import encoders
+from email.mime.nonmultipart import MIMENonMultipart
+
+
+class MIMEApplication(MIMENonMultipart):
+    """Class for generating application/* MIME documents."""
+
+    def __init__(self, _data, _subtype='octet-stream',
+                 _encoder=encoders.encode_base64, *, policy=None, **_params):
+        """Create an application/* type MIME document.
+
+        _data is a string containing the raw application data.
+
+        _subtype is the MIME content type subtype, defaulting to
+        'octet-stream'.
+
+        _encoder is a function which will perform the actual encoding for
+        transport of the application data, defaulting to base64 encoding.
+
+        Any additional keyword arguments are passed to the base class
+        constructor, which turns them into parameters on the Content-Type
+        header.
+        """
+        if _subtype is None:
+            raise TypeError('Invalid application MIME subtype')
+        MIMENonMultipart.__init__(self, 'application', _subtype, policy=policy,
+                                  **_params)
+        self.set_payload(_data)
+        _encoder(self)
diff --git a/contrib/tools/python3/src/Lib/email/mime/audio.py b/contrib/tools/python3/src/Lib/email/mime/audio.py
new file mode 100644
index 0000000000..4bcd7b224a
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/mime/audio.py
@@ -0,0 +1,74 @@
+# Copyright (C) 2001-2007 Python Software Foundation
+# Author: Anthony Baxter
+# Contact: email-sig@python.org
+
+"""Class representing audio/* type MIME documents."""
+
+__all__ = ['MIMEAudio']
+
+import sndhdr
+
+from io import BytesIO
+from email import encoders
+from email.mime.nonmultipart import MIMENonMultipart
+
+
+
+_sndhdr_MIMEmap = {'au'  : 'basic',
+                   'wav' :'x-wav',
+                   'aiff':'x-aiff',
+                   'aifc':'x-aiff',
+                   }
+
+# There are others in sndhdr that don't have MIME types. :(
+# Additional ones to be added to sndhdr? midi, mp3, realaudio, wma??
+def _whatsnd(data):
+    """Try to identify a sound file type.
+
+    sndhdr.what() has a pretty cruddy interface, unfortunately.  This is why
+    we re-do it here.  It would be easier to reverse engineer the Unix 'file'
+    command and use the standard 'magic' file, as shipped with a modern Unix.
+    """
+    hdr = data[:512]
+    fakefile = BytesIO(hdr)
+    for testfn in sndhdr.tests:
+        res = testfn(hdr, fakefile)
+        if res is not None:
+            return _sndhdr_MIMEmap.get(res[0])
+    return None
+
+
+
+class MIMEAudio(MIMENonMultipart):
+    """Class for generating audio/* MIME documents."""
+
+    def __init__(self, _audiodata, _subtype=None,
+                 _encoder=encoders.encode_base64, *, policy=None, **_params):
+        """Create an audio/* type MIME document.
+
+        _audiodata is a string containing the raw audio data.  If this data
+        can be decoded by the standard Python `sndhdr' module, then the
+        subtype will be automatically included in the Content-Type header.
+        Otherwise, you can specify  the specific audio subtype via the
+        _subtype parameter.  If _subtype is not given, and no subtype can be
+        guessed, a TypeError is raised.
+
+        _encoder is a function which will perform the actual encoding for
+        transport of the image data.  It takes one argument, which is this
+        Image instance.  It should use get_payload() and set_payload() to
+        change the payload to the encoded form.  It should also add any
+        Content-Transfer-Encoding or other headers to the message as
+        necessary.  The default encoding is Base64.
+
+        Any additional keyword arguments are passed to the base class
+        constructor, which turns them into parameters on the Content-Type
+        header.
+        """
+        if _subtype is None:
+            _subtype = _whatsnd(_audiodata)
+        if _subtype is None:
+            raise TypeError('Could not find audio MIME subtype')
+        MIMENonMultipart.__init__(self, 'audio', _subtype, policy=policy,
+                                  **_params)
+        self.set_payload(_audiodata)
+        _encoder(self)
diff --git a/contrib/tools/python3/src/Lib/email/mime/base.py b/contrib/tools/python3/src/Lib/email/mime/base.py
new file mode 100644
index 0000000000..1a3f9b51f6
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/mime/base.py
@@ -0,0 +1,30 @@
+# Copyright (C) 2001-2006 Python Software Foundation
+# Author: Barry Warsaw
+# Contact: email-sig@python.org
+
+"""Base class for MIME specializations."""
+
+__all__ = ['MIMEBase']
+
+import email.policy
+
+from email import message
+
+
+
+class MIMEBase(message.Message):
+    """Base class for MIME specializations."""
+
+    def __init__(self, _maintype, _subtype, *, policy=None, **_params):
+        """This constructor adds a Content-Type: and a MIME-Version: header.
+
+        The Content-Type: header is taken from the _maintype and _subtype
+        arguments.  Additional parameters for this header are taken from the
+        keyword arguments.
+        """
+        if policy is None:
+            policy = email.policy.compat32
+        message.Message.__init__(self, policy=policy)
+        ctype = '%s/%s' % (_maintype, _subtype)
+        self.add_header('Content-Type', ctype, **_params)
+        self['MIME-Version'] = '1.0'
diff --git a/contrib/tools/python3/src/Lib/email/mime/image.py b/contrib/tools/python3/src/Lib/email/mime/image.py
new file mode 100644
index 0000000000..92724643cd
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/mime/image.py
@@ -0,0 +1,47 @@
+# Copyright (C) 2001-2006 Python Software Foundation
+# Author: Barry Warsaw
+# Contact: email-sig@python.org
+
+"""Class representing image/* type MIME documents."""
+
+__all__ = ['MIMEImage']
+
+import imghdr
+
+from email import encoders
+from email.mime.nonmultipart import MIMENonMultipart
+
+
+
+class MIMEImage(MIMENonMultipart):
+    """Class for generating image/* type MIME documents."""
+
+    def __init__(self, _imagedata, _subtype=None,
+                 _encoder=encoders.encode_base64, *, policy=None, **_params):
+        """Create an image/* type MIME document.
+
+        _imagedata is a string containing the raw image data.  If this data
+        can be decoded by the standard Python `imghdr' module, then the
+        subtype will be automatically included in the Content-Type header.
+        Otherwise, you can specify the specific image subtype via the _subtype
+        parameter.
+
+        _encoder is a function which will perform the actual encoding for
+        transport of the image data.  It takes one argument, which is this
+        Image instance.  It should use get_payload() and set_payload() to
+        change the payload to the encoded form.  It should also add any
+        Content-Transfer-Encoding or other headers to the message as
+        necessary.  The default encoding is Base64.
+
+        Any additional keyword arguments are passed to the base class
+        constructor, which turns them into parameters on the Content-Type
+        header.
+        """
+        if _subtype is None:
+            _subtype = imghdr.what(None, _imagedata)
+        if _subtype is None:
+            raise TypeError('Could not guess image MIME subtype')
+        MIMENonMultipart.__init__(self, 'image', _subtype, policy=policy,
+                                  **_params)
+        self.set_payload(_imagedata)
+        _encoder(self)
diff --git a/contrib/tools/python3/src/Lib/email/mime/message.py b/contrib/tools/python3/src/Lib/email/mime/message.py
new file mode 100644
index 0000000000..07e4f2d119
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/mime/message.py
@@ -0,0 +1,34 @@
+# Copyright (C) 2001-2006 Python Software Foundation
+# Author: Barry Warsaw
+# Contact: email-sig@python.org
+
+"""Class representing message/* MIME documents."""
+
+__all__ = ['MIMEMessage']
+
+from email import message
+from email.mime.nonmultipart import MIMENonMultipart
+
+
+
+class MIMEMessage(MIMENonMultipart):
+    """Class representing message/* MIME documents."""
+
+    def __init__(self, _msg, _subtype='rfc822', *, policy=None):
+        """Create a message/* type MIME document.
+
+        _msg is a message object and must be an instance of Message, or a
+        derived class of Message, otherwise a TypeError is raised.
+
+        Optional _subtype defines the subtype of the contained message.  The
+        default is "rfc822" (this is defined by the MIME standard, even though
+        the term "rfc822" is technically outdated by RFC 2822).
+        """
+        MIMENonMultipart.__init__(self, 'message', _subtype, policy=policy)
+        if not isinstance(_msg, message.Message):
+            raise TypeError('Argument is not an instance of Message')
+        # It's convenient to use this base class method.  We need to do it
+        # this way or we'll get an exception
+        message.Message.attach(self, _msg)
+        # And be sure our default type is set correctly
+        self.set_default_type('message/rfc822')
diff --git a/contrib/tools/python3/src/Lib/email/mime/multipart.py b/contrib/tools/python3/src/Lib/email/mime/multipart.py
new file mode 100644
index 0000000000..2d3f288810
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/mime/multipart.py
@@ -0,0 +1,48 @@
+# Copyright (C) 2002-2006 Python Software Foundation
+# Author: Barry Warsaw
+# Contact: email-sig@python.org
+
+"""Base class for MIME multipart/* type messages."""
+
+__all__ = ['MIMEMultipart']
+
+from email.mime.base import MIMEBase
+
+
+
+class MIMEMultipart(MIMEBase):
+    """Base class for MIME multipart/* type messages."""
+
+    def __init__(self, _subtype='mixed', boundary=None, _subparts=None,
+                 *, policy=None,
+                 **_params):
+        """Creates a multipart/* type message.
+
+        By default, creates a multipart/mixed message, with proper
+        Content-Type and MIME-Version headers.
+
+        _subtype is the subtype of the multipart content type, defaulting to
+        `mixed'.
+
+        boundary is the multipart boundary string.  By default it is
+        calculated as needed.
+
+        _subparts is a sequence of initial subparts for the payload.  It
+        must be an iterable object, such as a list.  You can always
+        attach new subparts to the message by using the attach() method.
+
+        Additional parameters for the Content-Type header are taken from the
+        keyword arguments (or passed into the _params argument).
+        """
+        MIMEBase.__init__(self, 'multipart', _subtype, policy=policy, **_params)
+
+        # Initialise _payload to an empty list as the Message superclass's
+        # implementation of is_multipart assumes that _payload is a list for
+        # multipart messages.
+        self._payload = []
+
+        if _subparts:
+            for p in _subparts:
+                self.attach(p)
+        if boundary:
+            self.set_boundary(boundary)
diff --git a/contrib/tools/python3/src/Lib/email/mime/nonmultipart.py b/contrib/tools/python3/src/Lib/email/mime/nonmultipart.py
new file mode 100644
index 0000000000..e1f51968b5
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/mime/nonmultipart.py
@@ -0,0 +1,22 @@
+# Copyright (C) 2002-2006 Python Software Foundation
+# Author: Barry Warsaw
+# Contact: email-sig@python.org
+
+"""Base class for MIME type messages that are not multipart."""
+
+__all__ = ['MIMENonMultipart']
+
+from email import errors
+from email.mime.base import MIMEBase
+
+
+
+class MIMENonMultipart(MIMEBase):
+    """Base class for MIME non-multipart type messages."""
+
+    def attach(self, payload):
+        # The public API prohibits attaching multiple subparts to MIMEBase
+        # derived subtypes since none of them are, by definition, of content
+        # type multipart/*
+        raise errors.MultipartConversionError(
+            'Cannot attach additional subparts to non-multipart/*')
diff --git a/contrib/tools/python3/src/Lib/email/mime/text.py b/contrib/tools/python3/src/Lib/email/mime/text.py
new file mode 100644
index 0000000000..35b4423830
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/mime/text.py
@@ -0,0 +1,42 @@
+# Copyright (C) 2001-2006 Python Software Foundation
+# Author: Barry Warsaw
+# Contact: email-sig@python.org
+
+"""Class representing text/* type MIME documents."""
+
+__all__ = ['MIMEText']
+
+from email.charset import Charset
+from email.mime.nonmultipart import MIMENonMultipart
+
+
+
+class MIMEText(MIMENonMultipart):
+    """Class for generating text/* type MIME documents."""
+
+    def __init__(self, _text, _subtype='plain', _charset=None, *, policy=None):
+        """Create a text/* type MIME document.
+
+        _text is the string for this message object.
+
+        _subtype is the MIME sub content type, defaulting to "plain".
+
+        _charset is the character set parameter added to the Content-Type
+        header.  This defaults to "us-ascii".  Note that as a side-effect, the
+        Content-Transfer-Encoding header will also be set.
+        """
+
+        # If no _charset was specified, check to see if there are non-ascii
+        # characters present. If not, use 'us-ascii', otherwise use utf-8.
+        # XXX: This can be removed once #7304 is fixed.
+        if _charset is None:
+            try:
+                _text.encode('us-ascii')
+                _charset = 'us-ascii'
+            except UnicodeEncodeError:
+                _charset = 'utf-8'
+
+        MIMENonMultipart.__init__(self, 'text', _subtype, policy=policy,
+                                  **{'charset': str(_charset)})
+
+        self.set_payload(_text, _charset)
diff --git a/contrib/tools/python3/src/Lib/email/parser.py b/contrib/tools/python3/src/Lib/email/parser.py
new file mode 100644
index 0000000000..7db4da1ff0
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/parser.py
@@ -0,0 +1,131 @@
+# Copyright (C) 2001-2007 Python Software Foundation
+# Author: Barry Warsaw, Thomas Wouters, Anthony Baxter
+# Contact: email-sig@python.org
+
+"""A parser of RFC 2822 and MIME email messages."""
+
+__all__ = ['Parser', 'HeaderParser', 'BytesParser', 'BytesHeaderParser',
+           'FeedParser', 'BytesFeedParser']
+
+from io import StringIO, TextIOWrapper
+
+from email.feedparser import FeedParser, BytesFeedParser
+from email._policybase import compat32
+
+
+class Parser:
+    def __init__(self, _class=None, *, policy=compat32):
+        """Parser of RFC 2822 and MIME email messages.
+
+        Creates an in-memory object tree representing the email message, which
+        can then be manipulated and turned over to a Generator to return the
+        textual representation of the message.
+
+        The string must be formatted as a block of RFC 2822 headers and header
+        continuation lines, optionally preceded by a `Unix-from' header.  The
+        header block is terminated either by the end of the string or by a
+        blank line.
+
+        _class is the class to instantiate for new message objects when they
+        must be created.  This class must have a constructor that can take
+        zero arguments.  Default is Message.Message.
+
+        The policy keyword specifies a policy object that controls a number of
+        aspects of the parser's operation.  The default policy maintains
+        backward compatibility.
+
+        """
+        self._class = _class
+        self.policy = policy
+
+    def parse(self, fp, headersonly=False):
+        """Create a message structure from the data in a file.
+
+        Reads all the data from the file and returns the root of the message
+        structure.  Optional headersonly is a flag specifying whether to stop
+        parsing after reading the headers or not.  The default is False,
+        meaning it parses the entire contents of the file.
+        """
+        feedparser = FeedParser(self._class, policy=self.policy)
+        if headersonly:
+            feedparser._set_headersonly()
+        while True:
+            data = fp.read(8192)
+            if not data:
+                break
+            feedparser.feed(data)
+        return feedparser.close()
+
+    def parsestr(self, text, headersonly=False):
+        """Create a message structure from a string.
+
+        Returns the root of the message structure.  Optional headersonly is a
+        flag specifying whether to stop parsing after reading the headers or
+        not.  The default is False, meaning it parses the entire contents of
+        the file.
+        """
+        return self.parse(StringIO(text), headersonly=headersonly)
+
+
+
+class HeaderParser(Parser):
+    def parse(self, fp, headersonly=True):
+        return Parser.parse(self, fp, True)
+
+    def parsestr(self, text, headersonly=True):
+        return Parser.parsestr(self, text, True)
+
+
+class BytesParser:
+
+    def __init__(self, *args, **kw):
+        """Parser of binary RFC 2822 and MIME email messages.
+
+        Creates an in-memory object tree representing the email message, which
+        can then be manipulated and turned over to a Generator to return the
+        textual representation of the message.
+
+        The input must be formatted as a block of RFC 2822 headers and header
+        continuation lines, optionally preceded by a `Unix-from' header.  The
+        header block is terminated either by the end of the input or by a
+        blank line.
+
+        _class is the class to instantiate for new message objects when they
+        must be created.  This class must have a constructor that can take
+        zero arguments.  Default is Message.Message.
+        """
+        self.parser = Parser(*args, **kw)
+
+    def parse(self, fp, headersonly=False):
+        """Create a message structure from the data in a binary file.
+
+        Reads all the data from the file and returns the root of the message
+        structure.  Optional headersonly is a flag specifying whether to stop
+        parsing after reading the headers or not.  The default is False,
+        meaning it parses the entire contents of the file.
+        """
+        fp = TextIOWrapper(fp, encoding='ascii', errors='surrogateescape')
+        try:
+            return self.parser.parse(fp, headersonly)
+        finally:
+            fp.detach()
+
+
+    def parsebytes(self, text, headersonly=False):
+        """Create a message structure from a byte string.
+
+        Returns the root of the message structure.  Optional headersonly is a
+        flag specifying whether to stop parsing after reading the headers or
+        not.  The default is False, meaning it parses the entire contents of
+        the file.
+        """
+        text = text.decode('ASCII', errors='surrogateescape')
+        return self.parser.parsestr(text, headersonly)
+
+
+class BytesHeaderParser(BytesParser):
+    def parse(self, fp, headersonly=True):
+        return BytesParser.parse(self, fp, headersonly=True)
+
+    def parsebytes(self, text, headersonly=True):
+        return BytesParser.parsebytes(self, text, headersonly=True)
diff --git a/contrib/tools/python3/src/Lib/email/policy.py b/contrib/tools/python3/src/Lib/email/policy.py
new file mode 100644
index 0000000000..611deb50bb
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/policy.py
@@ -0,0 +1,224 @@
+"""This will be the home for the policy that hooks in the new
+code that adds all the email6 features.
+"""
+
+import re
+import sys
+from email._policybase import Policy, Compat32, compat32, _extend_docstrings
+from email.utils import _has_surrogates
+from email.headerregistry import HeaderRegistry as HeaderRegistry
+from email.contentmanager import raw_data_manager
+from email.message import EmailMessage
+
+__all__ = [
+    'Compat32',
+    'compat32',
+    'Policy',
+    'EmailPolicy',
+    'default',
+    'strict',
+    'SMTP',
+    'HTTP',
+    ]
+
+linesep_splitter = re.compile(r'\n|\r')
+
+@_extend_docstrings
+class EmailPolicy(Policy):
+
+    """+
+    PROVISIONAL
+
+    The API extensions enabled by this policy are currently provisional.
+    Refer to the documentation for details.
+
+    This policy adds new header parsing and folding algorithms.  Instead of
+    simple strings, headers are custom objects with custom attributes
+    depending on the type of the field.  The folding algorithm fully
+    implements RFCs 2047 and 5322.
+
+    In addition to the settable attributes listed above that apply to
+    all Policies, this policy adds the following additional attributes:
+
+    utf8                -- if False (the default) message headers will be
+                           serialized as ASCII, using encoded words to encode
+                           any non-ASCII characters in the source strings.  If
+                           True, the message headers will be serialized using
+                           utf8 and will not contain encoded words (see RFC
+                           6532 for more on this serialization format).
+
+    refold_source       -- if the value for a header in the Message object
+                           came from the parsing of some source, this attribute
+                           indicates whether or not a generator should refold
+                           that value when transforming the message back into
+                           stream form.  The possible values are:
+
+                           none  -- all source values use original folding
+                           long  -- source values that have any line that is
+                                    longer than max_line_length will be
+                                    refolded
+                           all  -- all values are refolded.
+
+                           The default is 'long'.
+
+    header_factory      -- a callable that takes two arguments, 'name' and
+                           'value', where 'name' is a header field name and
+                           'value' is an unfolded header field value, and
+                           returns a string-like object that represents that
+                           header.  A default header_factory is provided that
+                           understands some of the RFC5322 header field types.
+                           (Currently address fields and date fields have
+                           special treatment, while all other fields are
+                           treated as unstructured.  This list will be
+                           completed before the extension is marked stable.)
+
+    content_manager     -- an object with at least two methods: get_content
+                           and set_content.  When the get_content or
+                           set_content method of a Message object is called,
+                           it calls the corresponding method of this object,
+                           passing it the message object as its first argument,
+                           and any arguments or keywords that were passed to
+                           it as additional arguments.  The default
+                           content_manager is
+                           :data:`~email.contentmanager.raw_data_manager`.
+
+    """
+
+    message_factory = EmailMessage
+    utf8 = False
+    refold_source = 'long'
+    header_factory = HeaderRegistry()
+    content_manager = raw_data_manager
+
+    def __init__(self, **kw):
+        # Ensure that each new instance gets a unique header factory
+        # (as opposed to clones, which share the factory).
+        if 'header_factory' not in kw:
+            object.__setattr__(self, 'header_factory', HeaderRegistry())
+        super().__init__(**kw)
+
+    def header_max_count(self, name):
+        """+
+        The implementation for this class returns the max_count attribute from
+        the specialized header class that would be used to construct a header
+        of type 'name'.
+        """
+        return self.header_factory[name].max_count
+
+    # The logic of the next three methods is chosen such that it is possible to
+    # switch a Message object between a Compat32 policy and a policy derived
+    # from this class and have the results stay consistent.  This allows a
+    # Message object constructed with this policy to be passed to a library
+    # that only handles Compat32 objects, or to receive such an object and
+    # convert it to use the newer style by just changing its policy.  It is
+    # also chosen because it postpones the relatively expensive full rfc5322
+    # parse until as late as possible when parsing from source, since in many
+    # applications only a few headers will actually be inspected.
+
+    def header_source_parse(self, sourcelines):
+        """+
+        The name is parsed as everything up to the ':' and returned unmodified.
+        The value is determined by stripping leading whitespace off the
+        remainder of the first line, joining all subsequent lines together, and
+        stripping any trailing carriage return or linefeed characters.  (This
+        is the same as Compat32).
+
+        """
+        name, value = sourcelines[0].split(':', 1)
+        value = value.lstrip(' \t') + ''.join(sourcelines[1:])
+        return (name, value.rstrip('\r\n'))
+
+    def header_store_parse(self, name, value):
+        """+
+        The name is returned unchanged.  If the input value has a 'name'
+        attribute and it matches the name ignoring case, the value is returned
+        unchanged.  Otherwise the name and value are passed to header_factory
+        method, and the resulting custom header object is returned as the
+        value.  In this case a ValueError is raised if the input value contains
+        CR or LF characters.
+
+        """
+        if hasattr(value, 'name') and value.name.lower() == name.lower():
+            return (name, value)
+        if isinstance(value, str) and len(value.splitlines())>1:
+            # XXX this error message isn't quite right when we use splitlines
+            # (see issue 22233), but I'm not sure what should happen here.
+            raise ValueError("Header values may not contain linefeed "
+                             "or carriage return characters")
+        return (name, self.header_factory(name, value))
+
+    def header_fetch_parse(self, name, value):
+        """+
+        If the value has a 'name' attribute, it is returned to unmodified.
+        Otherwise the name and the value with any linesep characters removed
+        are passed to the header_factory method, and the resulting custom
+        header object is returned.  Any surrogateescaped bytes get turned
+        into the unicode unknown-character glyph.
+
+        """
+        if hasattr(value, 'name'):
+            return value
+        # We can't use splitlines here because it splits on more than \r and \n.
+        value = ''.join(linesep_splitter.split(value))
+        return self.header_factory(name, value)
+
+    def fold(self, name, value):
+        """+
+        Header folding is controlled by the refold_source policy setting.  A
+        value is considered to be a 'source value' if and only if it does not
+        have a 'name' attribute (having a 'name' attribute means it is a header
+        object of some sort).  If a source value needs to be refolded according
+        to the policy, it is converted into a custom header object by passing
+        the name and the value with any linesep characters removed to the
+        header_factory method.  Folding of a custom header object is done by
+        calling its fold method with the current policy.
+
+        Source values are split into lines using splitlines.  If the value is
+        not to be refolded, the lines are rejoined using the linesep from the
+        policy and returned.  The exception is lines containing non-ascii
+        binary data.  In that case the value is refolded regardless of the
+        refold_source setting, which causes the binary data to be CTE encoded
+        using the unknown-8bit charset.
+
+        """
+        return self._fold(name, value, refold_binary=True)
+
+    def fold_binary(self, name, value):
+        """+
+        The same as fold if cte_type is 7bit, except that the returned value is
+        bytes.
+
+        If cte_type is 8bit, non-ASCII binary data is converted back into
+        bytes.  Headers with binary data are not refolded, regardless of the
+        refold_header setting, since there is no way to know whether the binary
+        data consists of single byte characters or multibyte characters.
+
+        If utf8 is true, headers are encoded to utf8, otherwise to ascii with
+        non-ASCII unicode rendered as encoded words.
+
+        """
+        folded = self._fold(name, value, refold_binary=self.cte_type=='7bit')
+        charset = 'utf8' if self.utf8 else 'ascii'
+        return folded.encode(charset, 'surrogateescape')
+
+    def _fold(self, name, value, refold_binary=False):
+        if hasattr(value, 'name'):
+            return value.fold(policy=self)
+        maxlen = self.max_line_length if self.max_line_length else sys.maxsize
+        lines = value.splitlines()
+        refold = (self.refold_source == 'all' or
+                  self.refold_source == 'long' and
+                    (lines and len(lines[0])+len(name)+2 > maxlen or
+                     any(len(x) > maxlen for x in lines[1:])))
+        if refold or refold_binary and _has_surrogates(value):
+            return self.header_factory(name, ''.join(lines)).fold(policy=self)
+        return name + ': ' + self.linesep.join(lines) + self.linesep
+
+
+default = EmailPolicy()
+# Make the default policy use the class default header_factory
+del default.header_factory
+strict = default.clone(raise_on_defect=True)
+SMTP = default.clone(linesep='\r\n')
+HTTP = default.clone(linesep='\r\n', max_line_length=None)
+SMTPUTF8 = SMTP.clone(utf8=True)
diff --git a/contrib/tools/python3/src/Lib/email/quoprimime.py b/contrib/tools/python3/src/Lib/email/quoprimime.py
new file mode 100644
index 0000000000..94534f7ee1
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/quoprimime.py
@@ -0,0 +1,299 @@
+# Copyright (C) 2001-2006 Python Software Foundation
+# Author: Ben Gertzfield
+# Contact: email-sig@python.org
+
+"""Quoted-printable content transfer encoding per RFCs 2045-2047.
+
+This module handles the content transfer encoding method defined in RFC 2045
+to encode US ASCII-like 8-bit data called `quoted-printable'.  It is used to
+safely encode text that is in a character set similar to the 7-bit US ASCII
+character set, but that includes some 8-bit characters that are normally not
+allowed in email bodies or headers.
+
+Quoted-printable is very space-inefficient for encoding binary files; use the
+email.base64mime module for that instead.
+
+This module provides an interface to encode and decode both headers and bodies
+with quoted-printable encoding.
+
+RFC 2045 defines a method for including character set information in an
+`encoded-word' in a header.  This method is commonly used for 8-bit real names
+in To:/From:/Cc: etc. fields, as well as Subject: lines.
+
+This module does not do the line wrapping or end-of-line character
+conversion necessary for proper internationalized headers; it only
+does dumb encoding and decoding.  To deal with the various line
+wrapping issues, use the email.header module.
+"""
+
+__all__ = [
+    'body_decode',
+    'body_encode',
+    'body_length',
+    'decode',
+    'decodestring',
+    'header_decode',
+    'header_encode',
+    'header_length',
+    'quote',
+    'unquote',
+    ]
+
+import re
+
+from string import ascii_letters, digits, hexdigits
+
+CRLF = '\r\n'
+NL = '\n'
+EMPTYSTRING = ''
+
+# Build a mapping of octets to the expansion of that octet.  Since we're only
+# going to have 256 of these things, this isn't terribly inefficient
+# space-wise.  Remember that headers and bodies have different sets of safe
+# characters.  Initialize both maps with the full expansion, and then override
+# the safe bytes with the more compact form.
+_QUOPRI_MAP = ['=%02X' % c for c in range(256)]
+_QUOPRI_HEADER_MAP = _QUOPRI_MAP[:]
+_QUOPRI_BODY_MAP = _QUOPRI_MAP[:]
+
+# Safe header bytes which need no encoding.
+for c in b'-!*+/' + ascii_letters.encode('ascii') + digits.encode('ascii'):
+    _QUOPRI_HEADER_MAP[c] = chr(c)
+# Headers have one other special encoding; spaces become underscores.
+_QUOPRI_HEADER_MAP[ord(' ')] = '_'
+
+# Safe body bytes which need no encoding.
+for c in (b' !"#$%&\'()*+,-./0123456789:;<>'
+          b'?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`'
+          b'abcdefghijklmnopqrstuvwxyz{|}~\t'):
+    _QUOPRI_BODY_MAP[c] = chr(c)
+
+
+
+# Helpers
+def header_check(octet):
+    """Return True if the octet should be escaped with header quopri."""
+    return chr(octet) != _QUOPRI_HEADER_MAP[octet]
+
+
+def body_check(octet):
+    """Return True if the octet should be escaped with body quopri."""
+    return chr(octet) != _QUOPRI_BODY_MAP[octet]
+
+
+def header_length(bytearray):
+    """Return a header quoted-printable encoding length.
+
+    Note that this does not include any RFC 2047 chrome added by
+    `header_encode()`.
+
+    :param bytearray: An array of bytes (a.k.a. octets).
+    :return: The length in bytes of the byte array when it is encoded with
+        quoted-printable for headers.
+    """
+    return sum(len(_QUOPRI_HEADER_MAP[octet]) for octet in bytearray)
+
+
+def body_length(bytearray):
+    """Return a body quoted-printable encoding length.
+
+    :param bytearray: An array of bytes (a.k.a. octets).
+    :return: The length in bytes of the byte array when it is encoded with
+        quoted-printable for bodies.
+    """
+    return sum(len(_QUOPRI_BODY_MAP[octet]) for octet in bytearray)
+
+
+def _max_append(L, s, maxlen, extra=''):
+    if not isinstance(s, str):
+        s = chr(s)
+    if not L:
+        L.append(s.lstrip())
+    elif len(L[-1]) + len(s) <= maxlen:
+        L[-1] += extra + s
+    else:
+        L.append(s.lstrip())
+
+
+def unquote(s):
+    """Turn a string in the form =AB to the ASCII character with value 0xab"""
+    return chr(int(s[1:3], 16))
+
+
+def quote(c):
+    return _QUOPRI_MAP[ord(c)]
+
+
+def header_encode(header_bytes, charset='iso-8859-1'):
+    """Encode a single header line with quoted-printable (like) encoding.
+
+    Defined in RFC 2045, this `Q' encoding is similar to quoted-printable, but
+    used specifically for email header fields to allow charsets with mostly 7
+    bit characters (and some 8 bit) to remain more or less readable in non-RFC
+    2045 aware mail clients.
+
+    charset names the character set to use in the RFC 2046 header.  It
+    defaults to iso-8859-1.
+    """
+    # Return empty headers as an empty string.
+    if not header_bytes:
+        return ''
+    # Iterate over every byte, encoding if necessary.
+    encoded = header_bytes.decode('latin1').translate(_QUOPRI_HEADER_MAP)
+    # Now add the RFC chrome to each encoded chunk and glue the chunks
+    # together.
+    return '=?%s?q?%s?=' % (charset, encoded)
+
+
+_QUOPRI_BODY_ENCODE_MAP = _QUOPRI_BODY_MAP[:]
+for c in b'\r\n':
+    _QUOPRI_BODY_ENCODE_MAP[c] = chr(c)
+
+def body_encode(body, maxlinelen=76, eol=NL):
+    """Encode with quoted-printable, wrapping at maxlinelen characters.
+
+    Each line of encoded text will end with eol, which defaults to "\\n".  Set
+    this to "\\r\\n" if you will be using the result of this function directly
+    in an email.
+
+    Each line will be wrapped at, at most, maxlinelen characters before the
+    eol string (maxlinelen defaults to 76 characters, the maximum value
+    permitted by RFC 2045).  Long lines will have the 'soft line break'
+    quoted-printable character "=" appended to them, so the decoded text will
+    be identical to the original text.
+
+    The minimum maxlinelen is 4 to have room for a quoted character ("=XX")
+    followed by a soft line break.  Smaller values will generate a
+    ValueError.
+
+    """
+
+    if maxlinelen < 4:
+        raise ValueError("maxlinelen must be at least 4")
+    if not body:
+        return body
+
+    # quote special characters
+    body = body.translate(_QUOPRI_BODY_ENCODE_MAP)
+
+    soft_break = '=' + eol
+    # leave space for the '=' at the end of a line
+    maxlinelen1 = maxlinelen - 1
+
+    encoded_body = []
+    append = encoded_body.append
+
+    for line in body.splitlines():
+        # break up the line into pieces no longer than maxlinelen - 1
+        start = 0
+        laststart = len(line) - 1 - maxlinelen
+        while start <= laststart:
+            stop = start + maxlinelen1
+            # make sure we don't break up an escape sequence
+            if line[stop - 2] == '=':
+                append(line[start:stop - 1])
+                start = stop - 2
+            elif line[stop - 1] == '=':
+                append(line[start:stop])
+                start = stop - 1
+            else:
+                append(line[start:stop] + '=')
+                start = stop
+
+        # handle rest of line, special case if line ends in whitespace
+        if line and line[-1] in ' \t':
+            room = start - laststart
+            if room >= 3:
+                # It's a whitespace character at end-of-line, and we have room
+                # for the three-character quoted encoding.
+                q = quote(line[-1])
+            elif room == 2:
+                # There's room for the whitespace character and a soft break.
+                q = line[-1] + soft_break
+            else:
+                # There's room only for a soft break.  The quoted whitespace
+                # will be the only content on the subsequent line.
+                q = soft_break + quote(line[-1])
+            append(line[start:-1] + q)
+        else:
+            append(line[start:])
+
+    # add back final newline if present
+    if body[-1] in CRLF:
+        append('')
+
+    return eol.join(encoded_body)
+
+
+
+# BAW: I'm not sure if the intent was for the signature of this function to be
+# the same as base64MIME.decode() or not...
+def decode(encoded, eol=NL):
+    """Decode a quoted-printable string.
+
+    Lines are separated with eol, which defaults to \\n.
+    """
+    if not encoded:
+        return encoded
+    # BAW: see comment in encode() above.  Again, we're building up the
+    # decoded string with string concatenation, which could be done much more
+    # efficiently.
+    decoded = ''
+
+    for line in encoded.splitlines():
+        line = line.rstrip()
+        if not line:
+            decoded += eol
+            continue
+
+        i = 0
+        n = len(line)
+        while i < n:
+            c = line[i]
+            if c != '=':
+                decoded += c
+                i += 1
+            # Otherwise, c == "=".  Are we at the end of the line?  If so, add
+            # a soft line break.
+            elif i+1 == n:
+                i += 1
+                continue
+            # Decode if in form =AB
+            elif i+2 < n and line[i+1] in hexdigits and line[i+2] in hexdigits:
+                decoded += unquote(line[i:i+3])
+                i += 3
+            # Otherwise, not in form =AB, pass literally
+            else:
+                decoded += c
+                i += 1
+
+            if i == n:
+                decoded += eol
+    # Special case if original string did not end with eol
+    if encoded[-1] not in '\r\n' and decoded.endswith(eol):
+        decoded = decoded[:-1]
+    return decoded
+
+
+# For convenience and backwards compatibility w/ standard base64 module
+body_decode = decode
+decodestring = decode
+
+
+
+def _unquote_match(match):
+    """Turn a match in the form =AB to the ASCII character with value 0xab"""
+    s = match.group(0)
+    return unquote(s)
+
+
+# Header decoding is done a bit differently
+def header_decode(s):
+    """Decode a string encoded with RFC 2045 MIME header `Q' encoding.
+
+    This function does not parse a full MIME header value encoded with
+    quoted-printable (like =?iso-8859-1?q?Hello_World?=) -- please use
+    the high level email.header class for that functionality.
+    """
+    s = s.replace('_', ' ')
+    return re.sub(r'=[a-fA-F0-9]{2}', _unquote_match, s, flags=re.ASCII)
diff --git a/contrib/tools/python3/src/Lib/email/utils.py b/contrib/tools/python3/src/Lib/email/utils.py
new file mode 100644
index 0000000000..48d30160aa
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/email/utils.py
@@ -0,0 +1,368 @@
+# Copyright (C) 2001-2010 Python Software Foundation
+# Author: Barry Warsaw
+# Contact: email-sig@python.org
+
+"""Miscellaneous utilities."""
+
+__all__ = [
+    'collapse_rfc2231_value',
+    'decode_params',
+    'decode_rfc2231',
+    'encode_rfc2231',
+    'formataddr',
+    'formatdate',
+    'format_datetime',
+    'getaddresses',
+    'make_msgid',
+    'mktime_tz',
+    'parseaddr',
+    'parsedate',
+    'parsedate_tz',
+    'parsedate_to_datetime',
+    'unquote',
+    ]
+
+import os
+import re
+import time
+import random
+import socket
+import datetime
+import urllib.parse
+
+from email._parseaddr import quote
+from email._parseaddr import AddressList as _AddressList
+from email._parseaddr import mktime_tz
+
+from email._parseaddr import parsedate, parsedate_tz, _parsedate_tz
+
+# Intrapackage imports
+from email.charset import Charset
+
+COMMASPACE = ', '
+EMPTYSTRING = ''
+UEMPTYSTRING = ''
+CRLF = '\r\n'
+TICK = "'"
+
+specialsre = re.compile(r'[][\\()<>@,:;".]')
+escapesre = re.compile(r'[\\"]')
+
+def _has_surrogates(s):
+    """Return True if s contains surrogate-escaped binary data."""
+    # This check is based on the fact that unless there are surrogates, utf8
+    # (Python's default encoding) can encode any string.  This is the fastest
+    # way to check for surrogates, see issue 11454 for timings.
+    try:
+        s.encode()
+        return False
+    except UnicodeEncodeError:
+        return True
+
+# How to deal with a string containing bytes before handing it to the
+# application through the 'normal' interface.
+def _sanitize(string):
+    # Turn any escaped bytes into unicode 'unknown' char.  If the escaped
+    # bytes happen to be utf-8 they will instead get decoded, even if they
+    # were invalid in the charset the source was supposed to be in.  This
+    # seems like it is not a bad thing; a defect was still registered.
+    original_bytes = string.encode('utf-8', 'surrogateescape')
+    return original_bytes.decode('utf-8', 'replace')
+
+
+
+# Helpers
+
+def formataddr(pair, charset='utf-8'):
+    """The inverse of parseaddr(), this takes a 2-tuple of the form
+    (realname, email_address) and returns the string value suitable
+    for an RFC 2822 From, To or Cc header.
+
+    If the first element of pair is false, then the second element is
+    returned unmodified.
+
+    The optional charset is the character set that is used to encode
+    realname in case realname is not ASCII safe.  Can be an instance of str or
+    a Charset-like object which has a header_encode method.  Default is
+    'utf-8'.
+    """
+    name, address = pair
+    # The address MUST (per RFC) be ascii, so raise a UnicodeError if it isn't.
+    address.encode('ascii')
+    if name:
+        try:
+            name.encode('ascii')
+        except UnicodeEncodeError:
+            if isinstance(charset, str):
+                charset = Charset(charset)
+            encoded_name = charset.header_encode(name)
+            return "%s <%s>" % (encoded_name, address)
+        else:
+            quotes = ''
+            if specialsre.search(name):
+                quotes = '"'
+            name = escapesre.sub(r'\\\g<0>', name)
+            return '%s%s%s <%s>' % (quotes, name, quotes, address)
+    return address
+
+
+
+def getaddresses(fieldvalues):
+    """Return a list of (REALNAME, EMAIL) for each fieldvalue."""
+    all = COMMASPACE.join(str(v) for v in fieldvalues)
+    a = _AddressList(all)
+    return a.addresslist
+
+
+def _format_timetuple_and_zone(timetuple, zone):
+    return '%s, %02d %s %04d %02d:%02d:%02d %s' % (
+        ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'][timetuple[6]],
+        timetuple[2],
+        ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
+         'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'][timetuple[1] - 1],
+        timetuple[0], timetuple[3], timetuple[4], timetuple[5],
+        zone)
+
+def formatdate(timeval=None, localtime=False, usegmt=False):
+    """Returns a date string as specified by RFC 2822, e.g.:
+
+    Fri, 09 Nov 2001 01:08:47 -0000
+
+    Optional timeval if given is a floating point time value as accepted by
+    gmtime() and localtime(), otherwise the current time is used.
+
+    Optional localtime is a flag that when True, interprets timeval, and
+    returns a date relative to the local timezone instead of UTC, properly
+    taking daylight savings time into account.
+
+    Optional argument usegmt means that the timezone is written out as
+    an ascii string, not numeric one (so "GMT" instead of "+0000"). This
+    is needed for HTTP, and is only used when localtime==False.
+    """
+    # Note: we cannot use strftime() because that honors the locale and RFC
+    # 2822 requires that day and month names be the English abbreviations.
+    if timeval is None:
+        timeval = time.time()
+    if localtime or usegmt:
+        dt = datetime.datetime.fromtimestamp(timeval, datetime.timezone.utc)
+    else:
+        dt = datetime.datetime.utcfromtimestamp(timeval)
+    if localtime:
+        dt = dt.astimezone()
+        usegmt = False
+    return format_datetime(dt, usegmt)
+
+def format_datetime(dt, usegmt=False):
+    """Turn a datetime into a date string as specified in RFC 2822.
+
+    If usegmt is True, dt must be an aware datetime with an offset of zero.  In
+    this case 'GMT' will be rendered instead of the normal +0000 required by
+    RFC2822.  This is to support HTTP headers involving date stamps.
+    """
+    now = dt.timetuple()
+    if usegmt:
+        if dt.tzinfo is None or dt.tzinfo != datetime.timezone.utc:
+            raise ValueError("usegmt option requires a UTC datetime")
+        zone = 'GMT'
+    elif dt.tzinfo is None:
+        zone = '-0000'
+    else:
+        zone = dt.strftime("%z")
+    return _format_timetuple_and_zone(now, zone)
+
+
+def make_msgid(idstring=None, domain=None):
+    """Returns a string suitable for RFC 2822 compliant Message-ID, e.g:
+
+    <142480216486.20800.16526388040877946887@nightshade.la.mastaler.com>
+
+    Optional idstring if given is a string used to strengthen the
+    uniqueness of the message id.  Optional domain if given provides the
+    portion of the message id after the '@'.  It defaults to the locally
+    defined hostname.
+    """
+    timeval = int(time.time()*100)
+    pid = os.getpid()
+    randint = random.getrandbits(64)
+    if idstring is None:
+        idstring = ''
+    else:
+        idstring = '.' + idstring
+    if domain is None:
+        domain = socket.getfqdn()
+    msgid = '<%d.%d.%d%s@%s>' % (timeval, pid, randint, idstring, domain)
+    return msgid
+
+
+def parsedate_to_datetime(data):
+    *dtuple, tz = _parsedate_tz(data)
+    if tz is None:
+        return datetime.datetime(*dtuple[:6])
+    return datetime.datetime(*dtuple[:6],
+            tzinfo=datetime.timezone(datetime.timedelta(seconds=tz)))
+
+
+def parseaddr(addr):
+    """
+    Parse addr into its constituent realname and email address parts.
+
+    Return a tuple of realname and email address, unless the parse fails, in
+    which case return a 2-tuple of ('', '').
+    """
+    addrs = _AddressList(addr).addresslist
+    if not addrs:
+        return '', ''
+    return addrs[0]
+
+
+# rfc822.unquote() doesn't properly de-backslash-ify in Python pre-2.3.
+def unquote(str):
+    """Remove quotes from a string."""
+    if len(str) > 1:
+        if str.startswith('"') and str.endswith('"'):
+            return str[1:-1].replace('\\\\', '\\').replace('\\"', '"')
+        if str.startswith('<') and str.endswith('>'):
+            return str[1:-1]
+    return str
+
+
+
+# RFC2231-related functions - parameter encoding and decoding
+def decode_rfc2231(s):
+    """Decode string according to RFC 2231"""
+    parts = s.split(TICK, 2)
+    if len(parts) <= 2:
+        return None, None, s
+    return parts
+
+
+def encode_rfc2231(s, charset=None, language=None):
+    """Encode string according to RFC 2231.
+
+    If neither charset nor language is given, then s is returned as-is.  If
+    charset is given but not language, the string is encoded using the empty
+    string for language.
+    """
+    s = urllib.parse.quote(s, safe='', encoding=charset or 'ascii')
+    if charset is None and language is None:
+        return s
+    if language is None:
+        language = ''
+    return "%s'%s'%s" % (charset, language, s)
+
+
+rfc2231_continuation = re.compile(r'^(?P<name>\w+)\*((?P<num>[0-9]+)\*?)?$',
+    re.ASCII)
+
+def decode_params(params):
+    """Decode parameters list according to RFC 2231.
+
+    params is a sequence of 2-tuples containing (param name, string value).
+    """
+    new_params = [params[0]]
+    # Map parameter's name to a list of continuations.  The values are a
+    # 3-tuple of the continuation number, the string value, and a flag
+    # specifying whether a particular segment is %-encoded.
+    rfc2231_params = {}
+    for name, value in params[1:]:
+        encoded = name.endswith('*')
+        value = unquote(value)
+        mo = rfc2231_continuation.match(name)
+        if mo:
+            name, num = mo.group('name', 'num')
+            if num is not None:
+                num = int(num)
+            rfc2231_params.setdefault(name, []).append((num, value, encoded))
+        else:
+            new_params.append((name, '"%s"' % quote(value)))
+    if rfc2231_params:
+        for name, continuations in rfc2231_params.items():
+            value = []
+            extended = False
+            # Sort by number
+            continuations.sort()
+            # And now append all values in numerical order, converting
+            # %-encodings for the encoded segments.  If any of the
+            # continuation names ends in a *, then the entire string, after
+            # decoding segments and concatenating, must have the charset and
+            # language specifiers at the beginning of the string.
+            for num, s, encoded in continuations:
+                if encoded:
+                    # Decode as "latin-1", so the characters in s directly
+                    # represent the percent-encoded octet values.
+                    # collapse_rfc2231_value treats this as an octet sequence.
+                    s = urllib.parse.unquote(s, encoding="latin-1")
+                    extended = True
+                value.append(s)
+            value = quote(EMPTYSTRING.join(value))
+            if extended:
+                charset, language, value = decode_rfc2231(value)
+                new_params.append((name, (charset, language, '"%s"' % value)))
+            else:
+                new_params.append((name, '"%s"' % value))
+    return new_params
+
+def collapse_rfc2231_value(value, errors='replace',
+                           fallback_charset='us-ascii'):
+    if not isinstance(value, tuple) or len(value) != 3:
+        return unquote(value)
+    # While value comes to us as a unicode string, we need it to be a bytes
+    # object.  We do not want bytes() normal utf-8 decoder, we want a straight
+    # interpretation of the string as character bytes.
+    charset, language, text = value
+    if charset is None:
+        # Issue 17369: if charset/lang is None, decode_rfc2231 couldn't parse
+        # the value, so use the fallback_charset.
+        charset = fallback_charset
+    rawbytes = bytes(text, 'raw-unicode-escape')
+    try:
+        return str(rawbytes, charset, errors)
+    except LookupError:
+        # charset is not a known codec.
+        return unquote(text)
+
+
+#
+# datetime doesn't provide a localtime function yet, so provide one.  Code
+# adapted from the patch in issue 9527.  This may not be perfect, but it is
+# better than not having it.
+#
+
+def localtime(dt=None, isdst=-1):
+    """Return local time as an aware datetime object.
+
+    If called without arguments, return current time.  Otherwise *dt*
+    argument should be a datetime instance, and it is converted to the
+    local time zone according to the system time zone database.  If *dt* is
+    naive (that is, dt.tzinfo is None), it is assumed to be in local time.
+    In this case, a positive or zero value for *isdst* causes localtime to
+    presume initially that summer time (for example, Daylight Saving Time)
+    is or is not (respectively) in effect for the specified time.  A
+    negative value for *isdst* causes the localtime() function to attempt
+    to divine whether summer time is in effect for the specified time.
+
+    """
+    if dt is None:
+        return datetime.datetime.now(datetime.timezone.utc).astimezone()
+    if dt.tzinfo is not None:
+        return dt.astimezone()
+    # We have a naive datetime.  Convert to a (localtime) timetuple and pass to
+    # system mktime together with the isdst hint.  System mktime will return
+    # seconds since epoch.
+    tm = dt.timetuple()[:-1] + (isdst,)
+    seconds = time.mktime(tm)
+    localtm = time.localtime(seconds)
+    try:
+        delta = datetime.timedelta(seconds=localtm.tm_gmtoff)
+        tz = datetime.timezone(delta, localtm.tm_zone)
+    except AttributeError:
+        # Compute UTC offset and compare with the value implied by tm_isdst.
+        # If the values match, use the zone name implied by tm_isdst.
+        delta = dt - datetime.datetime(*time.gmtime(seconds)[:6])
+        dst = time.daylight and localtm.tm_isdst > 0
+        gmtoff = -(time.altzone if dst else time.timezone)
+        if delta == datetime.timedelta(seconds=gmtoff):
+            tz = datetime.timezone(delta, time.tzname[dst])
+        else:
+            tz = datetime.timezone(delta)
+    return dt.replace(tzinfo=tz)