fix ya.make

1 files changed, 0 insertions, 2151 deletions

diff --git a/contrib/tools/python3/src/Lib/mailbox.py b/contrib/tools/python3/src/Lib/mailbox.py
deleted file mode 100644
index 70da07ed2e..0000000000
--- a/contrib/tools/python3/src/Lib/mailbox.py
+++ /dev/null
@@ -1,2151 +0,0 @@
-"""Read/write support for Maildir, mbox, MH, Babyl, and MMDF mailboxes."""
-
-# Notes for authors of new mailbox subclasses:
-#
-# Remember to fsync() changes to disk before closing a modified file
-# or returning from a flush() method.  See functions _sync_flush() and
-# _sync_close().
-
-import os
-import time
-import calendar
-import socket
-import errno
-import copy
-import warnings
-import email
-import email.message
-import email.generator
-import io
-import contextlib
-from types import GenericAlias
-try:
-    import fcntl
-except ImportError:
-    fcntl = None
-
-__all__ = ['Mailbox', 'Maildir', 'mbox', 'MH', 'Babyl', 'MMDF',
-           'Message', 'MaildirMessage', 'mboxMessage', 'MHMessage',
-           'BabylMessage', 'MMDFMessage', 'Error', 'NoSuchMailboxError',
-           'NotEmptyError', 'ExternalClashError', 'FormatError']
-
-linesep = os.linesep.encode('ascii')
-
-class Mailbox:
-    """A group of messages in a particular place."""
-
-    def __init__(self, path, factory=None, create=True):
-        """Initialize a Mailbox instance."""
-        self._path = os.path.abspath(os.path.expanduser(path))
-        self._factory = factory
-
-    def add(self, message):
-        """Add message and return assigned key."""
-        raise NotImplementedError('Method must be implemented by subclass')
-
-    def remove(self, key):
-        """Remove the keyed message; raise KeyError if it doesn't exist."""
-        raise NotImplementedError('Method must be implemented by subclass')
-
-    def __delitem__(self, key):
-        self.remove(key)
-
-    def discard(self, key):
-        """If the keyed message exists, remove it."""
-        try:
-            self.remove(key)
-        except KeyError:
-            pass
-
-    def __setitem__(self, key, message):
-        """Replace the keyed message; raise KeyError if it doesn't exist."""
-        raise NotImplementedError('Method must be implemented by subclass')
-
-    def get(self, key, default=None):
-        """Return the keyed message, or default if it doesn't exist."""
-        try:
-            return self.__getitem__(key)
-        except KeyError:
-            return default
-
-    def __getitem__(self, key):
-        """Return the keyed message; raise KeyError if it doesn't exist."""
-        if not self._factory:
-            return self.get_message(key)
-        else:
-            with contextlib.closing(self.get_file(key)) as file:
-                return self._factory(file)
-
-    def get_message(self, key):
-        """Return a Message representation or raise a KeyError."""
-        raise NotImplementedError('Method must be implemented by subclass')
-
-    def get_string(self, key):
-        """Return a string representation or raise a KeyError.
-
-        Uses email.message.Message to create a 7bit clean string
-        representation of the message."""
-        return email.message_from_bytes(self.get_bytes(key)).as_string()
-
-    def get_bytes(self, key):
-        """Return a byte string representation or raise a KeyError."""
-        raise NotImplementedError('Method must be implemented by subclass')
-
-    def get_file(self, key):
-        """Return a file-like representation or raise a KeyError."""
-        raise NotImplementedError('Method must be implemented by subclass')
-
-    def iterkeys(self):
-        """Return an iterator over keys."""
-        raise NotImplementedError('Method must be implemented by subclass')
-
-    def keys(self):
-        """Return a list of keys."""
-        return list(self.iterkeys())
-
-    def itervalues(self):
-        """Return an iterator over all messages."""
-        for key in self.iterkeys():
-            try:
-                value = self[key]
-            except KeyError:
-                continue
-            yield value
-
-    def __iter__(self):
-        return self.itervalues()
-
-    def values(self):
-        """Return a list of messages. Memory intensive."""
-        return list(self.itervalues())
-
-    def iteritems(self):
-        """Return an iterator over (key, message) tuples."""
-        for key in self.iterkeys():
-            try:
-                value = self[key]
-            except KeyError:
-                continue
-            yield (key, value)
-
-    def items(self):
-        """Return a list of (key, message) tuples. Memory intensive."""
-        return list(self.iteritems())
-
-    def __contains__(self, key):
-        """Return True if the keyed message exists, False otherwise."""
-        raise NotImplementedError('Method must be implemented by subclass')
-
-    def __len__(self):
-        """Return a count of messages in the mailbox."""
-        raise NotImplementedError('Method must be implemented by subclass')
-
-    def clear(self):
-        """Delete all messages."""
-        for key in self.keys():
-            self.discard(key)
-
-    def pop(self, key, default=None):
-        """Delete the keyed message and return it, or default."""
-        try:
-            result = self[key]
-        except KeyError:
-            return default
-        self.discard(key)
-        return result
-
-    def popitem(self):
-        """Delete an arbitrary (key, message) pair and return it."""
-        for key in self.iterkeys():
-            return (key, self.pop(key))     # This is only run once.
-        else:
-            raise KeyError('No messages in mailbox')
-
-    def update(self, arg=None):
-        """Change the messages that correspond to certain keys."""
-        if hasattr(arg, 'iteritems'):
-            source = arg.iteritems()
-        elif hasattr(arg, 'items'):
-            source = arg.items()
-        else:
-            source = arg
-        bad_key = False
-        for key, message in source:
-            try:
-                self[key] = message
-            except KeyError:
-                bad_key = True
-        if bad_key:
-            raise KeyError('No message with key(s)')
-
-    def flush(self):
-        """Write any pending changes to the disk."""
-        raise NotImplementedError('Method must be implemented by subclass')
-
-    def lock(self):
-        """Lock the mailbox."""
-        raise NotImplementedError('Method must be implemented by subclass')
-
-    def unlock(self):
-        """Unlock the mailbox if it is locked."""
-        raise NotImplementedError('Method must be implemented by subclass')
-
-    def close(self):
-        """Flush and close the mailbox."""
-        raise NotImplementedError('Method must be implemented by subclass')
-
-    def _string_to_bytes(self, message):
-        # If a message is not 7bit clean, we refuse to handle it since it
-        # likely came from reading invalid messages in text mode, and that way
-        # lies mojibake.
-        try:
-            return message.encode('ascii')
-        except UnicodeError:
-            raise ValueError("String input must be ASCII-only; "
-                "use bytes or a Message instead")
-
-    # Whether each message must end in a newline
-    _append_newline = False
-
-    def _dump_message(self, message, target, mangle_from_=False):
-        # This assumes the target file is open in binary mode.
-        """Dump message contents to target file."""
-        if isinstance(message, email.message.Message):
-            buffer = io.BytesIO()
-            gen = email.generator.BytesGenerator(buffer, mangle_from_, 0)
-            gen.flatten(message)
-            buffer.seek(0)
-            data = buffer.read()
-            data = data.replace(b'\n', linesep)
-            target.write(data)
-            if self._append_newline and not data.endswith(linesep):
-                # Make sure the message ends with a newline
-                target.write(linesep)
-        elif isinstance(message, (str, bytes, io.StringIO)):
-            if isinstance(message, io.StringIO):
-                warnings.warn("Use of StringIO input is deprecated, "
-                    "use BytesIO instead", DeprecationWarning, 3)
-                message = message.getvalue()
-            if isinstance(message, str):
-                message = self._string_to_bytes(message)
-            if mangle_from_:
-                message = message.replace(b'\nFrom ', b'\n>From ')
-            message = message.replace(b'\n', linesep)
-            target.write(message)
-            if self._append_newline and not message.endswith(linesep):
-                # Make sure the message ends with a newline
-                target.write(linesep)
-        elif hasattr(message, 'read'):
-            if hasattr(message, 'buffer'):
-                warnings.warn("Use of text mode files is deprecated, "
-                    "use a binary mode file instead", DeprecationWarning, 3)
-                message = message.buffer
-            lastline = None
-            while True:
-                line = message.readline()
-                # Universal newline support.
-                if line.endswith(b'\r\n'):
-                    line = line[:-2] + b'\n'
-                elif line.endswith(b'\r'):
-                    line = line[:-1] + b'\n'
-                if not line:
-                    break
-                if mangle_from_ and line.startswith(b'From '):
-                    line = b'>From ' + line[5:]
-                line = line.replace(b'\n', linesep)
-                target.write(line)
-                lastline = line
-            if self._append_newline and lastline and not lastline.endswith(linesep):
-                # Make sure the message ends with a newline
-                target.write(linesep)
-        else:
-            raise TypeError('Invalid message type: %s' % type(message))
-
-    __class_getitem__ = classmethod(GenericAlias)
-
-
-class Maildir(Mailbox):
-    """A qmail-style Maildir mailbox."""
-
-    colon = ':'
-
-    def __init__(self, dirname, factory=None, create=True):
-        """Initialize a Maildir instance."""
-        Mailbox.__init__(self, dirname, factory, create)
-        self._paths = {
-            'tmp': os.path.join(self._path, 'tmp'),
-            'new': os.path.join(self._path, 'new'),
-            'cur': os.path.join(self._path, 'cur'),
-            }
-        if not os.path.exists(self._path):
-            if create:
-                os.mkdir(self._path, 0o700)
-                for path in self._paths.values():
-                    os.mkdir(path, 0o700)
-            else:
-                raise NoSuchMailboxError(self._path)
-        self._toc = {}
-        self._toc_mtimes = {'cur': 0, 'new': 0}
-        self._last_read = 0         # Records last time we read cur/new
-        self._skewfactor = 0.1      # Adjust if os/fs clocks are skewing
-
-    def add(self, message):
-        """Add message and return assigned key."""
-        tmp_file = self._create_tmp()
-        try:
-            self._dump_message(message, tmp_file)
-        except BaseException:
-            tmp_file.close()
-            os.remove(tmp_file.name)
-            raise
-        _sync_close(tmp_file)
-        if isinstance(message, MaildirMessage):
-            subdir = message.get_subdir()
-            suffix = self.colon + message.get_info()
-            if suffix == self.colon:
-                suffix = ''
-        else:
-            subdir = 'new'
-            suffix = ''
-        uniq = os.path.basename(tmp_file.name).split(self.colon)[0]
-        dest = os.path.join(self._path, subdir, uniq + suffix)
-        if isinstance(message, MaildirMessage):
-            os.utime(tmp_file.name,
-                     (os.path.getatime(tmp_file.name), message.get_date()))
-        # No file modification should be done after the file is moved to its
-        # final position in order to prevent race conditions with changes
-        # from other programs
-        try:
-            try:
-                os.link(tmp_file.name, dest)
-            except (AttributeError, PermissionError):
-                os.rename(tmp_file.name, dest)
-            else:
-                os.remove(tmp_file.name)
-        except OSError as e:
-            os.remove(tmp_file.name)
-            if e.errno == errno.EEXIST:
-                raise ExternalClashError('Name clash with existing message: %s'
-                                         % dest)
-            else:
-                raise
-        return uniq
-
-    def remove(self, key):
-        """Remove the keyed message; raise KeyError if it doesn't exist."""
-        os.remove(os.path.join(self._path, self._lookup(key)))
-
-    def discard(self, key):
-        """If the keyed message exists, remove it."""
-        # This overrides an inapplicable implementation in the superclass.
-        try:
-            self.remove(key)
-        except (KeyError, FileNotFoundError):
-            pass
-
-    def __setitem__(self, key, message):
-        """Replace the keyed message; raise KeyError if it doesn't exist."""
-        old_subpath = self._lookup(key)
-        temp_key = self.add(message)
-        temp_subpath = self._lookup(temp_key)
-        if isinstance(message, MaildirMessage):
-            # temp's subdir and suffix were specified by message.
-            dominant_subpath = temp_subpath
-        else:
-            # temp's subdir and suffix were defaults from add().
-            dominant_subpath = old_subpath
-        subdir = os.path.dirname(dominant_subpath)
-        if self.colon in dominant_subpath:
-            suffix = self.colon + dominant_subpath.split(self.colon)[-1]
-        else:
-            suffix = ''
-        self.discard(key)
-        tmp_path = os.path.join(self._path, temp_subpath)
-        new_path = os.path.join(self._path, subdir, key + suffix)
-        if isinstance(message, MaildirMessage):
-            os.utime(tmp_path,
-                     (os.path.getatime(tmp_path), message.get_date()))
-        # No file modification should be done after the file is moved to its
-        # final position in order to prevent race conditions with changes
-        # from other programs
-        os.rename(tmp_path, new_path)
-
-    def get_message(self, key):
-        """Return a Message representation or raise a KeyError."""
-        subpath = self._lookup(key)
-        with open(os.path.join(self._path, subpath), 'rb') as f:
-            if self._factory:
-                msg = self._factory(f)
-            else:
-                msg = MaildirMessage(f)
-        subdir, name = os.path.split(subpath)
-        msg.set_subdir(subdir)
-        if self.colon in name:
-            msg.set_info(name.split(self.colon)[-1])
-        msg.set_date(os.path.getmtime(os.path.join(self._path, subpath)))
-        return msg
-
-    def get_bytes(self, key):
-        """Return a bytes representation or raise a KeyError."""
-        with open(os.path.join(self._path, self._lookup(key)), 'rb') as f:
-            return f.read().replace(linesep, b'\n')
-
-    def get_file(self, key):
-        """Return a file-like representation or raise a KeyError."""
-        f = open(os.path.join(self._path, self._lookup(key)), 'rb')
-        return _ProxyFile(f)
-
-    def iterkeys(self):
-        """Return an iterator over keys."""
-        self._refresh()
-        for key in self._toc:
-            try:
-                self._lookup(key)
-            except KeyError:
-                continue
-            yield key
-
-    def __contains__(self, key):
-        """Return True if the keyed message exists, False otherwise."""
-        self._refresh()
-        return key in self._toc
-
-    def __len__(self):
-        """Return a count of messages in the mailbox."""
-        self._refresh()
-        return len(self._toc)
-
-    def flush(self):
-        """Write any pending changes to disk."""
-        # Maildir changes are always written immediately, so there's nothing
-        # to do.
-        pass
-
-    def lock(self):
-        """Lock the mailbox."""
-        return
-
-    def unlock(self):
-        """Unlock the mailbox if it is locked."""
-        return
-
-    def close(self):
-        """Flush and close the mailbox."""
-        return
-
-    def list_folders(self):
-        """Return a list of folder names."""
-        result = []
-        for entry in os.listdir(self._path):
-            if len(entry) > 1 and entry[0] == '.' and \
-               os.path.isdir(os.path.join(self._path, entry)):
-                result.append(entry[1:])
-        return result
-
-    def get_folder(self, folder):
-        """Return a Maildir instance for the named folder."""
-        return Maildir(os.path.join(self._path, '.' + folder),
-                       factory=self._factory,
-                       create=False)
-
-    def add_folder(self, folder):
-        """Create a folder and return a Maildir instance representing it."""
-        path = os.path.join(self._path, '.' + folder)
-        result = Maildir(path, factory=self._factory)
-        maildirfolder_path = os.path.join(path, 'maildirfolder')
-        if not os.path.exists(maildirfolder_path):
-            os.close(os.open(maildirfolder_path, os.O_CREAT | os.O_WRONLY,
-                0o666))
-        return result
-
-    def remove_folder(self, folder):
-        """Delete the named folder, which must be empty."""
-        path = os.path.join(self._path, '.' + folder)
-        for entry in os.listdir(os.path.join(path, 'new')) + \
-                     os.listdir(os.path.join(path, 'cur')):
-            if len(entry) < 1 or entry[0] != '.':
-                raise NotEmptyError('Folder contains message(s): %s' % folder)
-        for entry in os.listdir(path):
-            if entry != 'new' and entry != 'cur' and entry != 'tmp' and \
-               os.path.isdir(os.path.join(path, entry)):
-                raise NotEmptyError("Folder contains subdirectory '%s': %s" %
-                                    (folder, entry))
-        for root, dirs, files in os.walk(path, topdown=False):
-            for entry in files:
-                os.remove(os.path.join(root, entry))
-            for entry in dirs:
-                os.rmdir(os.path.join(root, entry))
-        os.rmdir(path)
-
-    def clean(self):
-        """Delete old files in "tmp"."""
-        now = time.time()
-        for entry in os.listdir(os.path.join(self._path, 'tmp')):
-            path = os.path.join(self._path, 'tmp', entry)
-            if now - os.path.getatime(path) > 129600:   # 60 * 60 * 36
-                os.remove(path)
-
-    _count = 1  # This is used to generate unique file names.
-
-    def _create_tmp(self):
-        """Create a file in the tmp subdirectory and open and return it."""
-        now = time.time()
-        hostname = socket.gethostname()
-        if '/' in hostname:
-            hostname = hostname.replace('/', r'\057')
-        if ':' in hostname:
-            hostname = hostname.replace(':', r'\072')
-        uniq = "%s.M%sP%sQ%s.%s" % (int(now), int(now % 1 * 1e6), os.getpid(),
-                                    Maildir._count, hostname)
-        path = os.path.join(self._path, 'tmp', uniq)
-        try:
-            os.stat(path)
-        except FileNotFoundError:
-            Maildir._count += 1
-            try:
-                return _create_carefully(path)
-            except FileExistsError:
-                pass
-
-        # Fall through to here if stat succeeded or open raised EEXIST.
-        raise ExternalClashError('Name clash prevented file creation: %s' %
-                                 path)
-
-    def _refresh(self):
-        """Update table of contents mapping."""
-        # If it has been less than two seconds since the last _refresh() call,
-        # we have to unconditionally re-read the mailbox just in case it has
-        # been modified, because os.path.mtime() has a 2 sec resolution in the
-        # most common worst case (FAT) and a 1 sec resolution typically.  This
-        # results in a few unnecessary re-reads when _refresh() is called
-        # multiple times in that interval, but once the clock ticks over, we
-        # will only re-read as needed.  Because the filesystem might be being
-        # served by an independent system with its own clock, we record and
-        # compare with the mtimes from the filesystem.  Because the other
-        # system's clock might be skewing relative to our clock, we add an
-        # extra delta to our wait.  The default is one tenth second, but is an
-        # instance variable and so can be adjusted if dealing with a
-        # particularly skewed or irregular system.
-        if time.time() - self._last_read > 2 + self._skewfactor:
-            refresh = False
-            for subdir in self._toc_mtimes:
-                mtime = os.path.getmtime(self._paths[subdir])
-                if mtime > self._toc_mtimes[subdir]:
-                    refresh = True
-                self._toc_mtimes[subdir] = mtime
-            if not refresh:
-                return
-        # Refresh toc
-        self._toc = {}
-        for subdir in self._toc_mtimes:
-            path = self._paths[subdir]
-            for entry in os.listdir(path):
-                p = os.path.join(path, entry)
-                if os.path.isdir(p):
-                    continue
-                uniq = entry.split(self.colon)[0]
-                self._toc[uniq] = os.path.join(subdir, entry)
-        self._last_read = time.time()
-
-    def _lookup(self, key):
-        """Use TOC to return subpath for given key, or raise a KeyError."""
-        try:
-            if os.path.exists(os.path.join(self._path, self._toc[key])):
-                return self._toc[key]
-        except KeyError:
-            pass
-        self._refresh()
-        try:
-            return self._toc[key]
-        except KeyError:
-            raise KeyError('No message with key: %s' % key) from None
-
-    # This method is for backward compatibility only.
-    def next(self):
-        """Return the next message in a one-time iteration."""
-        if not hasattr(self, '_onetime_keys'):
-            self._onetime_keys = self.iterkeys()
-        while True:
-            try:
-                return self[next(self._onetime_keys)]
-            except StopIteration:
-                return None
-            except KeyError:
-                continue
-
-
-class _singlefileMailbox(Mailbox):
-    """A single-file mailbox."""
-
-    def __init__(self, path, factory=None, create=True):
-        """Initialize a single-file mailbox."""
-        Mailbox.__init__(self, path, factory, create)
-        try:
-            f = open(self._path, 'rb+')
-        except OSError as e:
-            if e.errno == errno.ENOENT:
-                if create:
-                    f = open(self._path, 'wb+')
-                else:
-                    raise NoSuchMailboxError(self._path)
-            elif e.errno in (errno.EACCES, errno.EROFS):
-                f = open(self._path, 'rb')
-            else:
-                raise
-        self._file = f
-        self._toc = None
-        self._next_key = 0
-        self._pending = False       # No changes require rewriting the file.
-        self._pending_sync = False  # No need to sync the file
-        self._locked = False
-        self._file_length = None    # Used to record mailbox size
-
-    def add(self, message):
-        """Add message and return assigned key."""
-        self._lookup()
-        self._toc[self._next_key] = self._append_message(message)
-        self._next_key += 1
-        # _append_message appends the message to the mailbox file. We
-        # don't need a full rewrite + rename, sync is enough.
-        self._pending_sync = True
-        return self._next_key - 1
-
-    def remove(self, key):
-        """Remove the keyed message; raise KeyError if it doesn't exist."""
-        self._lookup(key)
-        del self._toc[key]
-        self._pending = True
-
-    def __setitem__(self, key, message):
-        """Replace the keyed message; raise KeyError if it doesn't exist."""
-        self._lookup(key)
-        self._toc[key] = self._append_message(message)
-        self._pending = True
-
-    def iterkeys(self):
-        """Return an iterator over keys."""
-        self._lookup()
-        yield from self._toc.keys()
-
-    def __contains__(self, key):
-        """Return True if the keyed message exists, False otherwise."""
-        self._lookup()
-        return key in self._toc
-
-    def __len__(self):
-        """Return a count of messages in the mailbox."""
-        self._lookup()
-        return len(self._toc)
-
-    def lock(self):
-        """Lock the mailbox."""
-        if not self._locked:
-            _lock_file(self._file)
-            self._locked = True
-
-    def unlock(self):
-        """Unlock the mailbox if it is locked."""
-        if self._locked:
-            _unlock_file(self._file)
-            self._locked = False
-
-    def flush(self):
-        """Write any pending changes to disk."""
-        if not self._pending:
-            if self._pending_sync:
-                # Messages have only been added, so syncing the file
-                # is enough.
-                _sync_flush(self._file)
-                self._pending_sync = False
-            return
-
-        # In order to be writing anything out at all, self._toc must
-        # already have been generated (and presumably has been modified
-        # by adding or deleting an item).
-        assert self._toc is not None
-
-        # Check length of self._file; if it's changed, some other process
-        # has modified the mailbox since we scanned it.
-        self._file.seek(0, 2)
-        cur_len = self._file.tell()
-        if cur_len != self._file_length:
-            raise ExternalClashError('Size of mailbox file changed '
-                                     '(expected %i, found %i)' %
-                                     (self._file_length, cur_len))
-
-        new_file = _create_temporary(self._path)
-        try:
-            new_toc = {}
-            self._pre_mailbox_hook(new_file)
-            for key in sorted(self._toc.keys()):
-                start, stop = self._toc[key]
-                self._file.seek(start)
-                self._pre_message_hook(new_file)
-                new_start = new_file.tell()
-                while True:
-                    buffer = self._file.read(min(4096,
-                                                 stop - self._file.tell()))
-                    if not buffer:
-                        break
-                    new_file.write(buffer)
-                new_toc[key] = (new_start, new_file.tell())
-                self._post_message_hook(new_file)
-            self._file_length = new_file.tell()
-        except:
-            new_file.close()
-            os.remove(new_file.name)
-            raise
-        _sync_close(new_file)
-        # self._file is about to get replaced, so no need to sync.
-        self._file.close()
-        # Make sure the new file's mode is the same as the old file's
-        mode = os.stat(self._path).st_mode
-        os.chmod(new_file.name, mode)
-        try:
-            os.rename(new_file.name, self._path)
-        except FileExistsError:
-            os.remove(self._path)
-            os.rename(new_file.name, self._path)
-        self._file = open(self._path, 'rb+')
-        self._toc = new_toc
-        self._pending = False
-        self._pending_sync = False
-        if self._locked:
-            _lock_file(self._file, dotlock=False)
-
-    def _pre_mailbox_hook(self, f):
-        """Called before writing the mailbox to file f."""
-        return
-
-    def _pre_message_hook(self, f):
-        """Called before writing each message to file f."""
-        return
-
-    def _post_message_hook(self, f):
-        """Called after writing each message to file f."""
-        return
-
-    def close(self):
-        """Flush and close the mailbox."""
-        try:
-            self.flush()
-        finally:
-            try:
-                if self._locked:
-                    self.unlock()
-            finally:
-                self._file.close()  # Sync has been done by self.flush() above.
-
-    def _lookup(self, key=None):
-        """Return (start, stop) or raise KeyError."""
-        if self._toc is None:
-            self._generate_toc()
-        if key is not None:
-            try:
-                return self._toc[key]
-            except KeyError:
-                raise KeyError('No message with key: %s' % key) from None
-
-    def _append_message(self, message):
-        """Append message to mailbox and return (start, stop) offsets."""
-        self._file.seek(0, 2)
-        before = self._file.tell()
-        if len(self._toc) == 0 and not self._pending:
-            # This is the first message, and the _pre_mailbox_hook
-            # hasn't yet been called. If self._pending is True,
-            # messages have been removed, so _pre_mailbox_hook must
-            # have been called already.
-            self._pre_mailbox_hook(self._file)
-        try:
-            self._pre_message_hook(self._file)
-            offsets = self._install_message(message)
-            self._post_message_hook(self._file)
-        except BaseException:
-            self._file.truncate(before)
-            raise
-        self._file.flush()
-        self._file_length = self._file.tell()  # Record current length of mailbox
-        return offsets
-
-
-
-class _mboxMMDF(_singlefileMailbox):
-    """An mbox or MMDF mailbox."""
-
-    _mangle_from_ = True
-
-    def get_message(self, key):
-        """Return a Message representation or raise a KeyError."""
-        start, stop = self._lookup(key)
-        self._file.seek(start)
-        from_line = self._file.readline().replace(linesep, b'')
-        string = self._file.read(stop - self._file.tell())
-        msg = self._message_factory(string.replace(linesep, b'\n'))
-        msg.set_from(from_line[5:].decode('ascii'))
-        return msg
-
-    def get_string(self, key, from_=False):
-        """Return a string representation or raise a KeyError."""
-        return email.message_from_bytes(
-            self.get_bytes(key, from_)).as_string(unixfrom=from_)
-
-    def get_bytes(self, key, from_=False):
-        """Return a string representation or raise a KeyError."""
-        start, stop = self._lookup(key)
-        self._file.seek(start)
-        if not from_:
-            self._file.readline()
-        string = self._file.read(stop - self._file.tell())
-        return string.replace(linesep, b'\n')
-
-    def get_file(self, key, from_=False):
-        """Return a file-like representation or raise a KeyError."""
-        start, stop = self._lookup(key)
-        self._file.seek(start)
-        if not from_:
-            self._file.readline()
-        return _PartialFile(self._file, self._file.tell(), stop)
-
-    def _install_message(self, message):
-        """Format a message and blindly write to self._file."""
-        from_line = None
-        if isinstance(message, str):
-            message = self._string_to_bytes(message)
-        if isinstance(message, bytes) and message.startswith(b'From '):
-            newline = message.find(b'\n')
-            if newline != -1:
-                from_line = message[:newline]
-                message = message[newline + 1:]
-            else:
-                from_line = message
-                message = b''
-        elif isinstance(message, _mboxMMDFMessage):
-            author = message.get_from().encode('ascii')
-            from_line = b'From ' + author
-        elif isinstance(message, email.message.Message):
-            from_line = message.get_unixfrom()  # May be None.
-            if from_line is not None:
-                from_line = from_line.encode('ascii')
-        if from_line is None:
-            from_line = b'From MAILER-DAEMON ' + time.asctime(time.gmtime()).encode()
-        start = self._file.tell()
-        self._file.write(from_line + linesep)
-        self._dump_message(message, self._file, self._mangle_from_)
-        stop = self._file.tell()
-        return (start, stop)
-
-
-class mbox(_mboxMMDF):
-    """A classic mbox mailbox."""
-
-    _mangle_from_ = True
-
-    # All messages must end in a newline character, and
-    # _post_message_hooks outputs an empty line between messages.
-    _append_newline = True
-
-    def __init__(self, path, factory=None, create=True):
-        """Initialize an mbox mailbox."""
-        self._message_factory = mboxMessage
-        _mboxMMDF.__init__(self, path, factory, create)
-
-    def _post_message_hook(self, f):
-        """Called after writing each message to file f."""
-        f.write(linesep)
-
-    def _generate_toc(self):
-        """Generate key-to-(start, stop) table of contents."""
-        starts, stops = [], []
-        last_was_empty = False
-        self._file.seek(0)
-        while True:
-            line_pos = self._file.tell()
-            line = self._file.readline()
-            if line.startswith(b'From '):
-                if len(stops) < len(starts):
-                    if last_was_empty:
-                        stops.append(line_pos - len(linesep))
-                    else:
-                        # The last line before the "From " line wasn't
-                        # blank, but we consider it a start of a
-                        # message anyway.
-                        stops.append(line_pos)
-                starts.append(line_pos)
-                last_was_empty = False
-            elif not line:
-                if last_was_empty:
-                    stops.append(line_pos - len(linesep))
-                else:
-                    stops.append(line_pos)
-                break
-            elif line == linesep:
-                last_was_empty = True
-            else:
-                last_was_empty = False
-        self._toc = dict(enumerate(zip(starts, stops)))
-        self._next_key = len(self._toc)
-        self._file_length = self._file.tell()
-
-
-class MMDF(_mboxMMDF):
-    """An MMDF mailbox."""
-
-    def __init__(self, path, factory=None, create=True):
-        """Initialize an MMDF mailbox."""
-        self._message_factory = MMDFMessage
-        _mboxMMDF.__init__(self, path, factory, create)
-
-    def _pre_message_hook(self, f):
-        """Called before writing each message to file f."""
-        f.write(b'\001\001\001\001' + linesep)
-
-    def _post_message_hook(self, f):
-        """Called after writing each message to file f."""
-        f.write(linesep + b'\001\001\001\001' + linesep)
-
-    def _generate_toc(self):
-        """Generate key-to-(start, stop) table of contents."""
-        starts, stops = [], []
-        self._file.seek(0)
-        next_pos = 0
-        while True:
-            line_pos = next_pos
-            line = self._file.readline()
-            next_pos = self._file.tell()
-            if line.startswith(b'\001\001\001\001' + linesep):
-                starts.append(next_pos)
-                while True:
-                    line_pos = next_pos
-                    line = self._file.readline()
-                    next_pos = self._file.tell()
-                    if line == b'\001\001\001\001' + linesep:
-                        stops.append(line_pos - len(linesep))
-                        break
-                    elif not line:
-                        stops.append(line_pos)
-                        break
-            elif not line:
-                break
-        self._toc = dict(enumerate(zip(starts, stops)))
-        self._next_key = len(self._toc)
-        self._file.seek(0, 2)
-        self._file_length = self._file.tell()
-
-
-class MH(Mailbox):
-    """An MH mailbox."""
-
-    def __init__(self, path, factory=None, create=True):
-        """Initialize an MH instance."""
-        Mailbox.__init__(self, path, factory, create)
-        if not os.path.exists(self._path):
-            if create:
-                os.mkdir(self._path, 0o700)
-                os.close(os.open(os.path.join(self._path, '.mh_sequences'),
-                                 os.O_CREAT | os.O_EXCL | os.O_WRONLY, 0o600))
-            else:
-                raise NoSuchMailboxError(self._path)
-        self._locked = False
-
-    def add(self, message):
-        """Add message and return assigned key."""
-        keys = self.keys()
-        if len(keys) == 0:
-            new_key = 1
-        else:
-            new_key = max(keys) + 1
-        new_path = os.path.join(self._path, str(new_key))
-        f = _create_carefully(new_path)
-        closed = False
-        try:
-            if self._locked:
-                _lock_file(f)
-            try:
-                try:
-                    self._dump_message(message, f)
-                except BaseException:
-                    # Unlock and close so it can be deleted on Windows
-                    if self._locked:
-                        _unlock_file(f)
-                    _sync_close(f)
-                    closed = True
-                    os.remove(new_path)
-                    raise
-                if isinstance(message, MHMessage):
-                    self._dump_sequences(message, new_key)
-            finally:
-                if self._locked:
-                    _unlock_file(f)
-        finally:
-            if not closed:
-                _sync_close(f)
-        return new_key
-
-    def remove(self, key):
-        """Remove the keyed message; raise KeyError if it doesn't exist."""
-        path = os.path.join(self._path, str(key))
-        try:
-            f = open(path, 'rb+')
-        except OSError as e:
-            if e.errno == errno.ENOENT:
-                raise KeyError('No message with key: %s' % key)
-            else:
-                raise
-        else:
-            f.close()
-            os.remove(path)
-
-    def __setitem__(self, key, message):
-        """Replace the keyed message; raise KeyError if it doesn't exist."""
-        path = os.path.join(self._path, str(key))
-        try:
-            f = open(path, 'rb+')
-        except OSError as e:
-            if e.errno == errno.ENOENT:
-                raise KeyError('No message with key: %s' % key)
-            else:
-                raise
-        try:
-            if self._locked:
-                _lock_file(f)
-            try:
-                os.close(os.open(path, os.O_WRONLY | os.O_TRUNC))
-                self._dump_message(message, f)
-                if isinstance(message, MHMessage):
-                    self._dump_sequences(message, key)
-            finally:
-                if self._locked:
-                    _unlock_file(f)
-        finally:
-            _sync_close(f)
-
-    def get_message(self, key):
-        """Return a Message representation or raise a KeyError."""
-        try:
-            if self._locked:
-                f = open(os.path.join(self._path, str(key)), 'rb+')
-            else:
-                f = open(os.path.join(self._path, str(key)), 'rb')
-        except OSError as e:
-            if e.errno == errno.ENOENT:
-                raise KeyError('No message with key: %s' % key)
-            else:
-                raise
-        with f:
-            if self._locked:
-                _lock_file(f)
-            try:
-                msg = MHMessage(f)
-            finally:
-                if self._locked:
-                    _unlock_file(f)
-        for name, key_list in self.get_sequences().items():
-            if key in key_list:
-                msg.add_sequence(name)
-        return msg
-
-    def get_bytes(self, key):
-        """Return a bytes representation or raise a KeyError."""
-        try:
-            if self._locked:
-                f = open(os.path.join(self._path, str(key)), 'rb+')
-            else:
-                f = open(os.path.join(self._path, str(key)), 'rb')
-        except OSError as e:
-            if e.errno == errno.ENOENT:
-                raise KeyError('No message with key: %s' % key)
-            else:
-                raise
-        with f:
-            if self._locked:
-                _lock_file(f)
-            try:
-                return f.read().replace(linesep, b'\n')
-            finally:
-                if self._locked:
-                    _unlock_file(f)
-
-    def get_file(self, key):
-        """Return a file-like representation or raise a KeyError."""
-        try:
-            f = open(os.path.join(self._path, str(key)), 'rb')
-        except OSError as e:
-            if e.errno == errno.ENOENT:
-                raise KeyError('No message with key: %s' % key)
-            else:
-                raise
-        return _ProxyFile(f)
-
-    def iterkeys(self):
-        """Return an iterator over keys."""
-        return iter(sorted(int(entry) for entry in os.listdir(self._path)
-                                      if entry.isdigit()))
-
-    def __contains__(self, key):
-        """Return True if the keyed message exists, False otherwise."""
-        return os.path.exists(os.path.join(self._path, str(key)))
-
-    def __len__(self):
-        """Return a count of messages in the mailbox."""
-        return len(list(self.iterkeys()))
-
-    def lock(self):
-        """Lock the mailbox."""
-        if not self._locked:
-            self._file = open(os.path.join(self._path, '.mh_sequences'), 'rb+')
-            _lock_file(self._file)
-            self._locked = True
-
-    def unlock(self):
-        """Unlock the mailbox if it is locked."""
-        if self._locked:
-            _unlock_file(self._file)
-            _sync_close(self._file)
-            del self._file
-            self._locked = False
-
-    def flush(self):
-        """Write any pending changes to the disk."""
-        return
-
-    def close(self):
-        """Flush and close the mailbox."""
-        if self._locked:
-            self.unlock()
-
-    def list_folders(self):
-        """Return a list of folder names."""
-        result = []
-        for entry in os.listdir(self._path):
-            if os.path.isdir(os.path.join(self._path, entry)):
-                result.append(entry)
-        return result
-
-    def get_folder(self, folder):
-        """Return an MH instance for the named folder."""
-        return MH(os.path.join(self._path, folder),
-                  factory=self._factory, create=False)
-
-    def add_folder(self, folder):
-        """Create a folder and return an MH instance representing it."""
-        return MH(os.path.join(self._path, folder),
-                  factory=self._factory)
-
-    def remove_folder(self, folder):
-        """Delete the named folder, which must be empty."""
-        path = os.path.join(self._path, folder)
-        entries = os.listdir(path)
-        if entries == ['.mh_sequences']:
-            os.remove(os.path.join(path, '.mh_sequences'))
-        elif entries == []:
-            pass
-        else:
-            raise NotEmptyError('Folder not empty: %s' % self._path)
-        os.rmdir(path)
-
-    def get_sequences(self):
-        """Return a name-to-key-list dictionary to define each sequence."""
-        results = {}
-        with open(os.path.join(self._path, '.mh_sequences'), 'r', encoding='ASCII') as f:
-            all_keys = set(self.keys())
-            for line in f:
-                try:
-                    name, contents = line.split(':')
-                    keys = set()
-                    for spec in contents.split():
-                        if spec.isdigit():
-                            keys.add(int(spec))
-                        else:
-                            start, stop = (int(x) for x in spec.split('-'))
-                            keys.update(range(start, stop + 1))
-                    results[name] = [key for key in sorted(keys) \
-                                         if key in all_keys]
-                    if len(results[name]) == 0:
-                        del results[name]
-                except ValueError:
-                    raise FormatError('Invalid sequence specification: %s' %
-                                      line.rstrip())
-        return results
-
-    def set_sequences(self, sequences):
-        """Set sequences using the given name-to-key-list dictionary."""
-        f = open(os.path.join(self._path, '.mh_sequences'), 'r+', encoding='ASCII')
-        try:
-            os.close(os.open(f.name, os.O_WRONLY | os.O_TRUNC))
-            for name, keys in sequences.items():
-                if len(keys) == 0:
-                    continue
-                f.write(name + ':')
-                prev = None
-                completing = False
-                for key in sorted(set(keys)):
-                    if key - 1 == prev:
-                        if not completing:
-                            completing = True
-                            f.write('-')
-                    elif completing:
-                        completing = False
-                        f.write('%s %s' % (prev, key))
-                    else:
-                        f.write(' %s' % key)
-                    prev = key
-                if completing:
-                    f.write(str(prev) + '\n')
-                else:
-                    f.write('\n')
-        finally:
-            _sync_close(f)
-
-    def pack(self):
-        """Re-name messages to eliminate numbering gaps. Invalidates keys."""
-        sequences = self.get_sequences()
-        prev = 0
-        changes = []
-        for key in self.iterkeys():
-            if key - 1 != prev:
-                changes.append((key, prev + 1))
-                try:
-                    os.link(os.path.join(self._path, str(key)),
-                            os.path.join(self._path, str(prev + 1)))
-                except (AttributeError, PermissionError):
-                    os.rename(os.path.join(self._path, str(key)),
-                              os.path.join(self._path, str(prev + 1)))
-                else:
-                    os.unlink(os.path.join(self._path, str(key)))
-            prev += 1
-        self._next_key = prev + 1
-        if len(changes) == 0:
-            return
-        for name, key_list in sequences.items():
-            for old, new in changes:
-                if old in key_list:
-                    key_list[key_list.index(old)] = new
-        self.set_sequences(sequences)
-
-    def _dump_sequences(self, message, key):
-        """Inspect a new MHMessage and update sequences appropriately."""
-        pending_sequences = message.get_sequences()
-        all_sequences = self.get_sequences()
-        for name, key_list in all_sequences.items():
-            if name in pending_sequences:
-                key_list.append(key)
-            elif key in key_list:
-                del key_list[key_list.index(key)]
-        for sequence in pending_sequences:
-            if sequence not in all_sequences:
-                all_sequences[sequence] = [key]
-        self.set_sequences(all_sequences)
-
-
-class Babyl(_singlefileMailbox):
-    """An Rmail-style Babyl mailbox."""
-
-    _special_labels = frozenset({'unseen', 'deleted', 'filed', 'answered',
-                                 'forwarded', 'edited', 'resent'})
-
-    def __init__(self, path, factory=None, create=True):
-        """Initialize a Babyl mailbox."""
-        _singlefileMailbox.__init__(self, path, factory, create)
-        self._labels = {}
-
-    def add(self, message):
-        """Add message and return assigned key."""
-        key = _singlefileMailbox.add(self, message)
-        if isinstance(message, BabylMessage):
-            self._labels[key] = message.get_labels()
-        return key
-
-    def remove(self, key):
-        """Remove the keyed message; raise KeyError if it doesn't exist."""
-        _singlefileMailbox.remove(self, key)
-        if key in self._labels:
-            del self._labels[key]
-
-    def __setitem__(self, key, message):
-        """Replace the keyed message; raise KeyError if it doesn't exist."""
-        _singlefileMailbox.__setitem__(self, key, message)
-        if isinstance(message, BabylMessage):
-            self._labels[key] = message.get_labels()
-
-    def get_message(self, key):
-        """Return a Message representation or raise a KeyError."""
-        start, stop = self._lookup(key)
-        self._file.seek(start)
-        self._file.readline()   # Skip b'1,' line specifying labels.
-        original_headers = io.BytesIO()
-        while True:
-            line = self._file.readline()
-            if line == b'*** EOOH ***' + linesep or not line:
-                break
-            original_headers.write(line.replace(linesep, b'\n'))
-        visible_headers = io.BytesIO()
-        while True:
-            line = self._file.readline()
-            if line == linesep or not line:
-                break
-            visible_headers.write(line.replace(linesep, b'\n'))
-        # Read up to the stop, or to the end
-        n = stop - self._file.tell()
-        assert n >= 0
-        body = self._file.read(n)
-        body = body.replace(linesep, b'\n')
-        msg = BabylMessage(original_headers.getvalue() + body)
-        msg.set_visible(visible_headers.getvalue())
-        if key in self._labels:
-            msg.set_labels(self._labels[key])
-        return msg
-
-    def get_bytes(self, key):
-        """Return a string representation or raise a KeyError."""
-        start, stop = self._lookup(key)
-        self._file.seek(start)
-        self._file.readline()   # Skip b'1,' line specifying labels.
-        original_headers = io.BytesIO()
-        while True:
-            line = self._file.readline()
-            if line == b'*** EOOH ***' + linesep or not line:
-                break
-            original_headers.write(line.replace(linesep, b'\n'))
-        while True:
-            line = self._file.readline()
-            if line == linesep or not line:
-                break
-        headers = original_headers.getvalue()
-        n = stop - self._file.tell()
-        assert n >= 0
-        data = self._file.read(n)
-        data = data.replace(linesep, b'\n')
-        return headers + data
-
-    def get_file(self, key):
-        """Return a file-like representation or raise a KeyError."""
-        return io.BytesIO(self.get_bytes(key).replace(b'\n', linesep))
-
-    def get_labels(self):
-        """Return a list of user-defined labels in the mailbox."""
-        self._lookup()
-        labels = set()
-        for label_list in self._labels.values():
-            labels.update(label_list)
-        labels.difference_update(self._special_labels)
-        return list(labels)
-
-    def _generate_toc(self):
-        """Generate key-to-(start, stop) table of contents."""
-        starts, stops = [], []
-        self._file.seek(0)
-        next_pos = 0
-        label_lists = []
-        while True:
-            line_pos = next_pos
-            line = self._file.readline()
-            next_pos = self._file.tell()
-            if line == b'\037\014' + linesep:
-                if len(stops) < len(starts):
-                    stops.append(line_pos - len(linesep))
-                starts.append(next_pos)
-                labels = [label.strip() for label
-                                        in self._file.readline()[1:].split(b',')
-                                        if label.strip()]
-                label_lists.append(labels)
-            elif line == b'\037' or line == b'\037' + linesep:
-                if len(stops) < len(starts):
-                    stops.append(line_pos - len(linesep))
-            elif not line:
-                stops.append(line_pos - len(linesep))
-                break
-        self._toc = dict(enumerate(zip(starts, stops)))
-        self._labels = dict(enumerate(label_lists))
-        self._next_key = len(self._toc)
-        self._file.seek(0, 2)
-        self._file_length = self._file.tell()
-
-    def _pre_mailbox_hook(self, f):
-        """Called before writing the mailbox to file f."""
-        babyl = b'BABYL OPTIONS:' + linesep
-        babyl += b'Version: 5' + linesep
-        labels = self.get_labels()
-        labels = (label.encode() for label in labels)
-        babyl += b'Labels:' + b','.join(labels) + linesep
-        babyl += b'\037'
-        f.write(babyl)
-
-    def _pre_message_hook(self, f):
-        """Called before writing each message to file f."""
-        f.write(b'\014' + linesep)
-
-    def _post_message_hook(self, f):
-        """Called after writing each message to file f."""
-        f.write(linesep + b'\037')
-
-    def _install_message(self, message):
-        """Write message contents and return (start, stop)."""
-        start = self._file.tell()
-        if isinstance(message, BabylMessage):
-            special_labels = []
-            labels = []
-            for label in message.get_labels():
-                if label in self._special_labels:
-                    special_labels.append(label)
-                else:
-                    labels.append(label)
-            self._file.write(b'1')
-            for label in special_labels:
-                self._file.write(b', ' + label.encode())
-            self._file.write(b',,')
-            for label in labels:
-                self._file.write(b' ' + label.encode() + b',')
-            self._file.write(linesep)
-        else:
-            self._file.write(b'1,,' + linesep)
-        if isinstance(message, email.message.Message):
-            orig_buffer = io.BytesIO()
-            orig_generator = email.generator.BytesGenerator(orig_buffer, False, 0)
-            orig_generator.flatten(message)
-            orig_buffer.seek(0)
-            while True:
-                line = orig_buffer.readline()
-                self._file.write(line.replace(b'\n', linesep))
-                if line == b'\n' or not line:
-                    break
-            self._file.write(b'*** EOOH ***' + linesep)
-            if isinstance(message, BabylMessage):
-                vis_buffer = io.BytesIO()
-                vis_generator = email.generator.BytesGenerator(vis_buffer, False, 0)
-                vis_generator.flatten(message.get_visible())
-                while True:
-                    line = vis_buffer.readline()
-                    self._file.write(line.replace(b'\n', linesep))
-                    if line == b'\n' or not line:
-                        break
-            else:
-                orig_buffer.seek(0)
-                while True:
-                    line = orig_buffer.readline()
-                    self._file.write(line.replace(b'\n', linesep))
-                    if line == b'\n' or not line:
-                        break
-            while True:
-                buffer = orig_buffer.read(4096) # Buffer size is arbitrary.
-                if not buffer:
-                    break
-                self._file.write(buffer.replace(b'\n', linesep))
-        elif isinstance(message, (bytes, str, io.StringIO)):
-            if isinstance(message, io.StringIO):
-                warnings.warn("Use of StringIO input is deprecated, "
-                    "use BytesIO instead", DeprecationWarning, 3)
-                message = message.getvalue()
-            if isinstance(message, str):
-                message = self._string_to_bytes(message)
-            body_start = message.find(b'\n\n') + 2
-            if body_start - 2 != -1:
-                self._file.write(message[:body_start].replace(b'\n', linesep))
-                self._file.write(b'*** EOOH ***' + linesep)
-                self._file.write(message[:body_start].replace(b'\n', linesep))
-                self._file.write(message[body_start:].replace(b'\n', linesep))
-            else:
-                self._file.write(b'*** EOOH ***' + linesep + linesep)
-                self._file.write(message.replace(b'\n', linesep))
-        elif hasattr(message, 'readline'):
-            if hasattr(message, 'buffer'):
-                warnings.warn("Use of text mode files is deprecated, "
-                    "use a binary mode file instead", DeprecationWarning, 3)
-                message = message.buffer
-            original_pos = message.tell()
-            first_pass = True
-            while True:
-                line = message.readline()
-                # Universal newline support.
-                if line.endswith(b'\r\n'):
-                    line = line[:-2] + b'\n'
-                elif line.endswith(b'\r'):
-                    line = line[:-1] + b'\n'
-                self._file.write(line.replace(b'\n', linesep))
-                if line == b'\n' or not line:
-                    if first_pass:
-                        first_pass = False
-                        self._file.write(b'*** EOOH ***' + linesep)
-                        message.seek(original_pos)
-                    else:
-                        break
-            while True:
-                line = message.readline()
-                if not line:
-                    break
-                # Universal newline support.
-                if line.endswith(b'\r\n'):
-                    line = line[:-2] + linesep
-                elif line.endswith(b'\r'):
-                    line = line[:-1] + linesep
-                elif line.endswith(b'\n'):
-                    line = line[:-1] + linesep
-                self._file.write(line)
-        else:
-            raise TypeError('Invalid message type: %s' % type(message))
-        stop = self._file.tell()
-        return (start, stop)
-
-
-class Message(email.message.Message):
-    """Message with mailbox-format-specific properties."""
-
-    def __init__(self, message=None):
-        """Initialize a Message instance."""
-        if isinstance(message, email.message.Message):
-            self._become_message(copy.deepcopy(message))
-            if isinstance(message, Message):
-                message._explain_to(self)
-        elif isinstance(message, bytes):
-            self._become_message(email.message_from_bytes(message))
-        elif isinstance(message, str):
-            self._become_message(email.message_from_string(message))
-        elif isinstance(message, io.TextIOWrapper):
-            self._become_message(email.message_from_file(message))
-        elif hasattr(message, "read"):
-            self._become_message(email.message_from_binary_file(message))
-        elif message is None:
-            email.message.Message.__init__(self)
-        else:
-            raise TypeError('Invalid message type: %s' % type(message))
-
-    def _become_message(self, message):
-        """Assume the non-format-specific state of message."""
-        type_specific = getattr(message, '_type_specific_attributes', [])
-        for name in message.__dict__:
-            if name not in type_specific:
-                self.__dict__[name] = message.__dict__[name]
-
-    def _explain_to(self, message):
-        """Copy format-specific state to message insofar as possible."""
-        if isinstance(message, Message):
-            return  # There's nothing format-specific to explain.
-        else:
-            raise TypeError('Cannot convert to specified type')
-
-
-class MaildirMessage(Message):
-    """Message with Maildir-specific properties."""
-
-    _type_specific_attributes = ['_subdir', '_info', '_date']
-
-    def __init__(self, message=None):
-        """Initialize a MaildirMessage instance."""
-        self._subdir = 'new'
-        self._info = ''
-        self._date = time.time()
-        Message.__init__(self, message)
-
-    def get_subdir(self):
-        """Return 'new' or 'cur'."""
-        return self._subdir
-
-    def set_subdir(self, subdir):
-        """Set subdir to 'new' or 'cur'."""
-        if subdir == 'new' or subdir == 'cur':
-            self._subdir = subdir
-        else:
-            raise ValueError("subdir must be 'new' or 'cur': %s" % subdir)
-
-    def get_flags(self):
-        """Return as a string the flags that are set."""
-        if self._info.startswith('2,'):
-            return self._info[2:]
-        else:
-            return ''
-
-    def set_flags(self, flags):
-        """Set the given flags and unset all others."""
-        self._info = '2,' + ''.join(sorted(flags))
-
-    def add_flag(self, flag):
-        """Set the given flag(s) without changing others."""
-        self.set_flags(''.join(set(self.get_flags()) | set(flag)))
-
-    def remove_flag(self, flag):
-        """Unset the given string flag(s) without changing others."""
-        if self.get_flags():
-            self.set_flags(''.join(set(self.get_flags()) - set(flag)))
-
-    def get_date(self):
-        """Return delivery date of message, in seconds since the epoch."""
-        return self._date
-
-    def set_date(self, date):
-        """Set delivery date of message, in seconds since the epoch."""
-        try:
-            self._date = float(date)
-        except ValueError:
-            raise TypeError("can't convert to float: %s" % date) from None
-
-    def get_info(self):
-        """Get the message's "info" as a string."""
-        return self._info
-
-    def set_info(self, info):
-        """Set the message's "info" string."""
-        if isinstance(info, str):
-            self._info = info
-        else:
-            raise TypeError('info must be a string: %s' % type(info))
-
-    def _explain_to(self, message):
-        """Copy Maildir-specific state to message insofar as possible."""
-        if isinstance(message, MaildirMessage):
-            message.set_flags(self.get_flags())
-            message.set_subdir(self.get_subdir())
-            message.set_date(self.get_date())
-        elif isinstance(message, _mboxMMDFMessage):
-            flags = set(self.get_flags())
-            if 'S' in flags:
-                message.add_flag('R')
-            if self.get_subdir() == 'cur':
-                message.add_flag('O')
-            if 'T' in flags:
-                message.add_flag('D')
-            if 'F' in flags:
-                message.add_flag('F')
-            if 'R' in flags:
-                message.add_flag('A')
-            message.set_from('MAILER-DAEMON', time.gmtime(self.get_date()))
-        elif isinstance(message, MHMessage):
-            flags = set(self.get_flags())
-            if 'S' not in flags:
-                message.add_sequence('unseen')
-            if 'R' in flags:
-                message.add_sequence('replied')
-            if 'F' in flags:
-                message.add_sequence('flagged')
-        elif isinstance(message, BabylMessage):
-            flags = set(self.get_flags())
-            if 'S' not in flags:
-                message.add_label('unseen')
-            if 'T' in flags:
-                message.add_label('deleted')
-            if 'R' in flags:
-                message.add_label('answered')
-            if 'P' in flags:
-                message.add_label('forwarded')
-        elif isinstance(message, Message):
-            pass
-        else:
-            raise TypeError('Cannot convert to specified type: %s' %
-                            type(message))
-
-
-class _mboxMMDFMessage(Message):
-    """Message with mbox- or MMDF-specific properties."""
-
-    _type_specific_attributes = ['_from']
-
-    def __init__(self, message=None):
-        """Initialize an mboxMMDFMessage instance."""
-        self.set_from('MAILER-DAEMON', True)
-        if isinstance(message, email.message.Message):
-            unixfrom = message.get_unixfrom()
-            if unixfrom is not None and unixfrom.startswith('From '):
-                self.set_from(unixfrom[5:])
-        Message.__init__(self, message)
-
-    def get_from(self):
-        """Return contents of "From " line."""
-        return self._from
-
-    def set_from(self, from_, time_=None):
-        """Set "From " line, formatting and appending time_ if specified."""
-        if time_ is not None:
-            if time_ is True:
-                time_ = time.gmtime()
-            from_ += ' ' + time.asctime(time_)
-        self._from = from_
-
-    def get_flags(self):
-        """Return as a string the flags that are set."""
-        return self.get('Status', '') + self.get('X-Status', '')
-
-    def set_flags(self, flags):
-        """Set the given flags and unset all others."""
-        flags = set(flags)
-        status_flags, xstatus_flags = '', ''
-        for flag in ('R', 'O'):
-            if flag in flags:
-                status_flags += flag
-                flags.remove(flag)
-        for flag in ('D', 'F', 'A'):
-            if flag in flags:
-                xstatus_flags += flag
-                flags.remove(flag)
-        xstatus_flags += ''.join(sorted(flags))
-        try:
-            self.replace_header('Status', status_flags)
-        except KeyError:
-            self.add_header('Status', status_flags)
-        try:
-            self.replace_header('X-Status', xstatus_flags)
-        except KeyError:
-            self.add_header('X-Status', xstatus_flags)
-
-    def add_flag(self, flag):
-        """Set the given flag(s) without changing others."""
-        self.set_flags(''.join(set(self.get_flags()) | set(flag)))
-
-    def remove_flag(self, flag):
-        """Unset the given string flag(s) without changing others."""
-        if 'Status' in self or 'X-Status' in self:
-            self.set_flags(''.join(set(self.get_flags()) - set(flag)))
-
-    def _explain_to(self, message):
-        """Copy mbox- or MMDF-specific state to message insofar as possible."""
-        if isinstance(message, MaildirMessage):
-            flags = set(self.get_flags())
-            if 'O' in flags:
-                message.set_subdir('cur')
-            if 'F' in flags:
-                message.add_flag('F')
-            if 'A' in flags:
-                message.add_flag('R')
-            if 'R' in flags:
-                message.add_flag('S')
-            if 'D' in flags:
-                message.add_flag('T')
-            del message['status']
-            del message['x-status']
-            maybe_date = ' '.join(self.get_from().split()[-5:])
-            try:
-                message.set_date(calendar.timegm(time.strptime(maybe_date,
-                                                      '%a %b %d %H:%M:%S %Y')))
-            except (ValueError, OverflowError):
-                pass
-        elif isinstance(message, _mboxMMDFMessage):
-            message.set_flags(self.get_flags())
-            message.set_from(self.get_from())
-        elif isinstance(message, MHMessage):
-            flags = set(self.get_flags())
-            if 'R' not in flags:
-                message.add_sequence('unseen')
-            if 'A' in flags:
-                message.add_sequence('replied')
-            if 'F' in flags:
-                message.add_sequence('flagged')
-            del message['status']
-            del message['x-status']
-        elif isinstance(message, BabylMessage):
-            flags = set(self.get_flags())
-            if 'R' not in flags:
-                message.add_label('unseen')
-            if 'D' in flags:
-                message.add_label('deleted')
-            if 'A' in flags:
-                message.add_label('answered')
-            del message['status']
-            del message['x-status']
-        elif isinstance(message, Message):
-            pass
-        else:
-            raise TypeError('Cannot convert to specified type: %s' %
-                            type(message))
-
-
-class mboxMessage(_mboxMMDFMessage):
-    """Message with mbox-specific properties."""
-
-
-class MHMessage(Message):
-    """Message with MH-specific properties."""
-
-    _type_specific_attributes = ['_sequences']
-
-    def __init__(self, message=None):
-        """Initialize an MHMessage instance."""
-        self._sequences = []
-        Message.__init__(self, message)
-
-    def get_sequences(self):
-        """Return a list of sequences that include the message."""
-        return self._sequences[:]
-
-    def set_sequences(self, sequences):
-        """Set the list of sequences that include the message."""
-        self._sequences = list(sequences)
-
-    def add_sequence(self, sequence):
-        """Add sequence to list of sequences including the message."""
-        if isinstance(sequence, str):
-            if not sequence in self._sequences:
-                self._sequences.append(sequence)
-        else:
-            raise TypeError('sequence type must be str: %s' % type(sequence))
-
-    def remove_sequence(self, sequence):
-        """Remove sequence from the list of sequences including the message."""
-        try:
-            self._sequences.remove(sequence)
-        except ValueError:
-            pass
-
-    def _explain_to(self, message):
-        """Copy MH-specific state to message insofar as possible."""
-        if isinstance(message, MaildirMessage):
-            sequences = set(self.get_sequences())
-            if 'unseen' in sequences:
-                message.set_subdir('cur')
-            else:
-                message.set_subdir('cur')
-                message.add_flag('S')
-            if 'flagged' in sequences:
-                message.add_flag('F')
-            if 'replied' in sequences:
-                message.add_flag('R')
-        elif isinstance(message, _mboxMMDFMessage):
-            sequences = set(self.get_sequences())
-            if 'unseen' not in sequences:
-                message.add_flag('RO')
-            else:
-                message.add_flag('O')
-            if 'flagged' in sequences:
-                message.add_flag('F')
-            if 'replied' in sequences:
-                message.add_flag('A')
-        elif isinstance(message, MHMessage):
-            for sequence in self.get_sequences():
-                message.add_sequence(sequence)
-        elif isinstance(message, BabylMessage):
-            sequences = set(self.get_sequences())
-            if 'unseen' in sequences:
-                message.add_label('unseen')
-            if 'replied' in sequences:
-                message.add_label('answered')
-        elif isinstance(message, Message):
-            pass
-        else:
-            raise TypeError('Cannot convert to specified type: %s' %
-                            type(message))
-
-
-class BabylMessage(Message):
-    """Message with Babyl-specific properties."""
-
-    _type_specific_attributes = ['_labels', '_visible']
-
-    def __init__(self, message=None):
-        """Initialize a BabylMessage instance."""
-        self._labels = []
-        self._visible = Message()
-        Message.__init__(self, message)
-
-    def get_labels(self):
-        """Return a list of labels on the message."""
-        return self._labels[:]
-
-    def set_labels(self, labels):
-        """Set the list of labels on the message."""
-        self._labels = list(labels)
-
-    def add_label(self, label):
-        """Add label to list of labels on the message."""
-        if isinstance(label, str):
-            if label not in self._labels:
-                self._labels.append(label)
-        else:
-            raise TypeError('label must be a string: %s' % type(label))
-
-    def remove_label(self, label):
-        """Remove label from the list of labels on the message."""
-        try:
-            self._labels.remove(label)
-        except ValueError:
-            pass
-
-    def get_visible(self):
-        """Return a Message representation of visible headers."""
-        return Message(self._visible)
-
-    def set_visible(self, visible):
-        """Set the Message representation of visible headers."""
-        self._visible = Message(visible)
-
-    def update_visible(self):
-        """Update and/or sensibly generate a set of visible headers."""
-        for header in self._visible.keys():
-            if header in self:
-                self._visible.replace_header(header, self[header])
-            else:
-                del self._visible[header]
-        for header in ('Date', 'From', 'Reply-To', 'To', 'CC', 'Subject'):
-            if header in self and header not in self._visible:
-                self._visible[header] = self[header]
-
-    def _explain_to(self, message):
-        """Copy Babyl-specific state to message insofar as possible."""
-        if isinstance(message, MaildirMessage):
-            labels = set(self.get_labels())
-            if 'unseen' in labels:
-                message.set_subdir('cur')
-            else:
-                message.set_subdir('cur')
-                message.add_flag('S')
-            if 'forwarded' in labels or 'resent' in labels:
-                message.add_flag('P')
-            if 'answered' in labels:
-                message.add_flag('R')
-            if 'deleted' in labels:
-                message.add_flag('T')
-        elif isinstance(message, _mboxMMDFMessage):
-            labels = set(self.get_labels())
-            if 'unseen' not in labels:
-                message.add_flag('RO')
-            else:
-                message.add_flag('O')
-            if 'deleted' in labels:
-                message.add_flag('D')
-            if 'answered' in labels:
-                message.add_flag('A')
-        elif isinstance(message, MHMessage):
-            labels = set(self.get_labels())
-            if 'unseen' in labels:
-                message.add_sequence('unseen')
-            if 'answered' in labels:
-                message.add_sequence('replied')
-        elif isinstance(message, BabylMessage):
-            message.set_visible(self.get_visible())
-            for label in self.get_labels():
-                message.add_label(label)
-        elif isinstance(message, Message):
-            pass
-        else:
-            raise TypeError('Cannot convert to specified type: %s' %
-                            type(message))
-
-
-class MMDFMessage(_mboxMMDFMessage):
-    """Message with MMDF-specific properties."""
-
-
-class _ProxyFile:
-    """A read-only wrapper of a file."""
-
-    def __init__(self, f, pos=None):
-        """Initialize a _ProxyFile."""
-        self._file = f
-        if pos is None:
-            self._pos = f.tell()
-        else:
-            self._pos = pos
-
-    def read(self, size=None):
-        """Read bytes."""
-        return self._read(size, self._file.read)
-
-    def read1(self, size=None):
-        """Read bytes."""
-        return self._read(size, self._file.read1)
-
-    def readline(self, size=None):
-        """Read a line."""
-        return self._read(size, self._file.readline)
-
-    def readlines(self, sizehint=None):
-        """Read multiple lines."""
-        result = []
-        for line in self:
-            result.append(line)
-            if sizehint is not None:
-                sizehint -= len(line)
-                if sizehint <= 0:
-                    break
-        return result
-
-    def __iter__(self):
-        """Iterate over lines."""
-        while True:
-            line = self.readline()
-            if not line:
-                return
-            yield line
-
-    def tell(self):
-        """Return the position."""
-        return self._pos
-
-    def seek(self, offset, whence=0):
-        """Change position."""
-        if whence == 1:
-            self._file.seek(self._pos)
-        self._file.seek(offset, whence)
-        self._pos = self._file.tell()
-
-    def close(self):
-        """Close the file."""
-        if hasattr(self, '_file'):
-            try:
-                if hasattr(self._file, 'close'):
-                    self._file.close()
-            finally:
-                del self._file
-
-    def _read(self, size, read_method):
-        """Read size bytes using read_method."""
-        if size is None:
-            size = -1
-        self._file.seek(self._pos)
-        result = read_method(size)
-        self._pos = self._file.tell()
-        return result
-
-    def __enter__(self):
-        """Context management protocol support."""
-        return self
-
-    def __exit__(self, *exc):
-        self.close()
-
-    def readable(self):
-        return self._file.readable()
-
-    def writable(self):
-        return self._file.writable()
-
-    def seekable(self):
-        return self._file.seekable()
-
-    def flush(self):
-        return self._file.flush()
-
-    @property
-    def closed(self):
-        if not hasattr(self, '_file'):
-            return True
-        if not hasattr(self._file, 'closed'):
-            return False
-        return self._file.closed
-
-    __class_getitem__ = classmethod(GenericAlias)
-
-
-class _PartialFile(_ProxyFile):
-    """A read-only wrapper of part of a file."""
-
-    def __init__(self, f, start=None, stop=None):
-        """Initialize a _PartialFile."""
-        _ProxyFile.__init__(self, f, start)
-        self._start = start
-        self._stop = stop
-
-    def tell(self):
-        """Return the position with respect to start."""
-        return _ProxyFile.tell(self) - self._start
-
-    def seek(self, offset, whence=0):
-        """Change position, possibly with respect to start or stop."""
-        if whence == 0:
-            self._pos = self._start
-            whence = 1
-        elif whence == 2:
-            self._pos = self._stop
-            whence = 1
-        _ProxyFile.seek(self, offset, whence)
-
-    def _read(self, size, read_method):
-        """Read size bytes using read_method, honoring start and stop."""
-        remaining = self._stop - self._pos
-        if remaining <= 0:
-            return b''
-        if size is None or size < 0 or size > remaining:
-            size = remaining
-        return _ProxyFile._read(self, size, read_method)
-
-    def close(self):
-        # do *not* close the underlying file object for partial files,
-        # since it's global to the mailbox object
-        if hasattr(self, '_file'):
-            del self._file
-
-
-def _lock_file(f, dotlock=True):
-    """Lock file f using lockf and dot locking."""
-    dotlock_done = False
-    try:
-        if fcntl:
-            try:
-                fcntl.lockf(f, fcntl.LOCK_EX | fcntl.LOCK_NB)
-            except OSError as e:
-                if e.errno in (errno.EAGAIN, errno.EACCES, errno.EROFS):
-                    raise ExternalClashError('lockf: lock unavailable: %s' %
-                                             f.name)
-                else:
-                    raise
-        if dotlock:
-            try:
-                pre_lock = _create_temporary(f.name + '.lock')
-                pre_lock.close()
-            except OSError as e:
-                if e.errno in (errno.EACCES, errno.EROFS):
-                    return  # Without write access, just skip dotlocking.
-                else:
-                    raise
-            try:
-                try:
-                    os.link(pre_lock.name, f.name + '.lock')
-                    dotlock_done = True
-                except (AttributeError, PermissionError):
-                    os.rename(pre_lock.name, f.name + '.lock')
-                    dotlock_done = True
-                else:
-                    os.unlink(pre_lock.name)
-            except FileExistsError:
-                os.remove(pre_lock.name)
-                raise ExternalClashError('dot lock unavailable: %s' %
-                                         f.name)
-    except:
-        if fcntl:
-            fcntl.lockf(f, fcntl.LOCK_UN)
-        if dotlock_done:
-            os.remove(f.name + '.lock')
-        raise
-
-def _unlock_file(f):
-    """Unlock file f using lockf and dot locking."""
-    if fcntl:
-        fcntl.lockf(f, fcntl.LOCK_UN)
-    if os.path.exists(f.name + '.lock'):
-        os.remove(f.name + '.lock')
-
-def _create_carefully(path):
-    """Create a file if it doesn't exist and open for reading and writing."""
-    fd = os.open(path, os.O_CREAT | os.O_EXCL | os.O_RDWR, 0o666)
-    try:
-        return open(path, 'rb+')
-    finally:
-        os.close(fd)
-
-def _create_temporary(path):
-    """Create a temp file based on path and open for reading and writing."""
-    return _create_carefully('%s.%s.%s.%s' % (path, int(time.time()),
-                                              socket.gethostname(),
-                                              os.getpid()))
-
-def _sync_flush(f):
-    """Ensure changes to file f are physically on disk."""
-    f.flush()
-    if hasattr(os, 'fsync'):
-        os.fsync(f.fileno())
-
-def _sync_close(f):
-    """Close file f, ensuring all changes are physically on disk."""
-    _sync_flush(f)
-    f.close()
-
-
-class Error(Exception):
-    """Raised for module-specific errors."""
-
-class NoSuchMailboxError(Error):
-    """The specified mailbox does not exist and won't be created."""
-
-class NotEmptyError(Error):
-    """The specified mailbox is not empty and deletion was requested."""
-
-class ExternalClashError(Error):
-    """Another process caused an action to fail."""
-
-class FormatError(Error):
-    """A file appears to have an invalid format."""