intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 1464 insertions, 0 deletions

diff --git a/contrib/tools/python3/src/Lib/shutil.py b/contrib/tools/python3/src/Lib/shutil.py
new file mode 100644
index 0000000000..752900c588
--- /dev/null
+++ b/contrib/tools/python3/src/Lib/shutil.py
@@ -0,0 +1,1464 @@
+"""Utility functions for copying and archiving files and directory trees.
+
+XXX The functions here don't copy the resource fork or other metadata on Mac.
+
+"""
+
+import os
+import sys
+import stat
+import fnmatch
+import collections
+import errno
+
+try:
+    import zlib
+    del zlib
+    _ZLIB_SUPPORTED = True
+except ImportError:
+    _ZLIB_SUPPORTED = False
+
+try:
+    import bz2
+    del bz2
+    _BZ2_SUPPORTED = True
+except ImportError:
+    _BZ2_SUPPORTED = False
+
+try:
+    import lzma
+    del lzma
+    _LZMA_SUPPORTED = True
+except ImportError:
+    _LZMA_SUPPORTED = False
+
+try:
+    from pwd import getpwnam
+except ImportError:
+    getpwnam = None
+
+try:
+    from grp import getgrnam
+except ImportError:
+    getgrnam = None
+
+_WINDOWS = os.name == 'nt'
+posix = nt = None
+if os.name == 'posix':
+    import posix
+elif _WINDOWS:
+    import nt
+
+COPY_BUFSIZE = 1024 * 1024 if _WINDOWS else 64 * 1024
+_USE_CP_SENDFILE = hasattr(os, "sendfile") and sys.platform.startswith("linux")
+_HAS_FCOPYFILE = posix and hasattr(posix, "_fcopyfile")  # macOS
+
+# CMD defaults in Windows 10
+_WIN_DEFAULT_PATHEXT = ".COM;.EXE;.BAT;.CMD;.VBS;.JS;.WS;.MSC"
+
+__all__ = ["copyfileobj", "copyfile", "copymode", "copystat", "copy", "copy2",
+           "copytree", "move", "rmtree", "Error", "SpecialFileError",
+           "ExecError", "make_archive", "get_archive_formats",
+           "register_archive_format", "unregister_archive_format",
+           "get_unpack_formats", "register_unpack_format",
+           "unregister_unpack_format", "unpack_archive",
+           "ignore_patterns", "chown", "which", "get_terminal_size",
+           "SameFileError"]
+           # disk_usage is added later, if available on the platform
+
+class Error(OSError):
+    pass
+
+class SameFileError(Error):
+    """Raised when source and destination are the same file."""
+
+class SpecialFileError(OSError):
+    """Raised when trying to do a kind of operation (e.g. copying) which is
+    not supported on a special file (e.g. a named pipe)"""
+
+class ExecError(OSError):
+    """Raised when a command could not be executed"""
+
+class ReadError(OSError):
+    """Raised when an archive cannot be read"""
+
+class RegistryError(Exception):
+    """Raised when a registry operation with the archiving
+    and unpacking registries fails"""
+
+class _GiveupOnFastCopy(Exception):
+    """Raised as a signal to fallback on using raw read()/write()
+    file copy when fast-copy functions fail to do so.
+    """
+
+def _fastcopy_fcopyfile(fsrc, fdst, flags):
+    """Copy a regular file content or metadata by using high-performance
+    fcopyfile(3) syscall (macOS).
+    """
+    try:
+        infd = fsrc.fileno()
+        outfd = fdst.fileno()
+    except Exception as err:
+        raise _GiveupOnFastCopy(err)  # not a regular file
+
+    try:
+        posix._fcopyfile(infd, outfd, flags)
+    except OSError as err:
+        err.filename = fsrc.name
+        err.filename2 = fdst.name
+        if err.errno in {errno.EINVAL, errno.ENOTSUP}:
+            raise _GiveupOnFastCopy(err)
+        else:
+            raise err from None
+
+def _fastcopy_sendfile(fsrc, fdst):
+    """Copy data from one regular mmap-like fd to another by using
+    high-performance sendfile(2) syscall.
+    This should work on Linux >= 2.6.33 only.
+    """
+    # Note: copyfileobj() is left alone in order to not introduce any
+    # unexpected breakage. Possible risks by using zero-copy calls
+    # in copyfileobj() are:
+    # - fdst cannot be open in "a"(ppend) mode
+    # - fsrc and fdst may be open in "t"(ext) mode
+    # - fsrc may be a BufferedReader (which hides unread data in a buffer),
+    #   GzipFile (which decompresses data), HTTPResponse (which decodes
+    #   chunks).
+    # - possibly others (e.g. encrypted fs/partition?)
+    global _USE_CP_SENDFILE
+    try:
+        infd = fsrc.fileno()
+        outfd = fdst.fileno()
+    except Exception as err:
+        raise _GiveupOnFastCopy(err)  # not a regular file
+
+    # Hopefully the whole file will be copied in a single call.
+    # sendfile() is called in a loop 'till EOF is reached (0 return)
+    # so a bufsize smaller or bigger than the actual file size
+    # should not make any difference, also in case the file content
+    # changes while being copied.
+    try:
+        blocksize = max(os.fstat(infd).st_size, 2 ** 23)  # min 8MiB
+    except OSError:
+        blocksize = 2 ** 27  # 128MiB
+    # On 32-bit architectures truncate to 1GiB to avoid OverflowError,
+    # see bpo-38319.
+    if sys.maxsize < 2 ** 32:
+        blocksize = min(blocksize, 2 ** 30)
+
+    offset = 0
+    while True:
+        try:
+            sent = os.sendfile(outfd, infd, offset, blocksize)
+        except OSError as err:
+            # ...in oder to have a more informative exception.
+            err.filename = fsrc.name
+            err.filename2 = fdst.name
+
+            if err.errno == errno.ENOTSOCK:
+                # sendfile() on this platform (probably Linux < 2.6.33)
+                # does not support copies between regular files (only
+                # sockets).
+                _USE_CP_SENDFILE = False
+                raise _GiveupOnFastCopy(err)
+
+            if err.errno == errno.ENOSPC:  # filesystem is full
+                raise err from None
+
+            # Give up on first call and if no data was copied.
+            if offset == 0 and os.lseek(outfd, 0, os.SEEK_CUR) == 0:
+                raise _GiveupOnFastCopy(err)
+
+            raise err
+        else:
+            if sent == 0:
+                break  # EOF
+            offset += sent
+
+def _copyfileobj_readinto(fsrc, fdst, length=COPY_BUFSIZE):
+    """readinto()/memoryview() based variant of copyfileobj().
+    *fsrc* must support readinto() method and both files must be
+    open in binary mode.
+    """
+    # Localize variable access to minimize overhead.
+    fsrc_readinto = fsrc.readinto
+    fdst_write = fdst.write
+    with memoryview(bytearray(length)) as mv:
+        while True:
+            n = fsrc_readinto(mv)
+            if not n:
+                break
+            elif n < length:
+                with mv[:n] as smv:
+                    fdst.write(smv)
+            else:
+                fdst_write(mv)
+
+def copyfileobj(fsrc, fdst, length=0):
+    """copy data from file-like object fsrc to file-like object fdst"""
+    # Localize variable access to minimize overhead.
+    if not length:
+        length = COPY_BUFSIZE
+    fsrc_read = fsrc.read
+    fdst_write = fdst.write
+    while True:
+        buf = fsrc_read(length)
+        if not buf:
+            break
+        fdst_write(buf)
+
+def _samefile(src, dst):
+    # Macintosh, Unix.
+    if isinstance(src, os.DirEntry) and hasattr(os.path, 'samestat'):
+        try:
+            return os.path.samestat(src.stat(), os.stat(dst))
+        except OSError:
+            return False
+
+    if hasattr(os.path, 'samefile'):
+        try:
+            return os.path.samefile(src, dst)
+        except OSError:
+            return False
+
+    # All other platforms: check for same pathname.
+    return (os.path.normcase(os.path.abspath(src)) ==
+            os.path.normcase(os.path.abspath(dst)))
+
+def _stat(fn):
+    return fn.stat() if isinstance(fn, os.DirEntry) else os.stat(fn)
+
+def _islink(fn):
+    return fn.is_symlink() if isinstance(fn, os.DirEntry) else os.path.islink(fn)
+
+def copyfile(src, dst, *, follow_symlinks=True):
+    """Copy data from src to dst in the most efficient way possible.
+
+    If follow_symlinks is not set and src is a symbolic link, a new
+    symlink will be created instead of copying the file it points to.
+
+    """
+    sys.audit("shutil.copyfile", src, dst)
+
+    if _samefile(src, dst):
+        raise SameFileError("{!r} and {!r} are the same file".format(src, dst))
+
+    file_size = 0
+    for i, fn in enumerate([src, dst]):
+        try:
+            st = _stat(fn)
+        except OSError:
+            # File most likely does not exist
+            pass
+        else:
+            # XXX What about other special files? (sockets, devices...)
+            if stat.S_ISFIFO(st.st_mode):
+                fn = fn.path if isinstance(fn, os.DirEntry) else fn
+                raise SpecialFileError("`%s` is a named pipe" % fn)
+            if _WINDOWS and i == 0:
+                file_size = st.st_size
+
+    if not follow_symlinks and _islink(src):
+        os.symlink(os.readlink(src), dst)
+    else:
+        with open(src, 'rb') as fsrc:
+            try:
+                with open(dst, 'wb') as fdst:
+                    # macOS
+                    if _HAS_FCOPYFILE:
+                        try:
+                            _fastcopy_fcopyfile(fsrc, fdst, posix._COPYFILE_DATA)
+                            return dst
+                        except _GiveupOnFastCopy:
+                            pass
+                    # Linux
+                    elif _USE_CP_SENDFILE:
+                        try:
+                            _fastcopy_sendfile(fsrc, fdst)
+                            return dst
+                        except _GiveupOnFastCopy:
+                            pass
+                    # Windows, see:
+                    # https://github.com/python/cpython/pull/7160#discussion_r195405230
+                    elif _WINDOWS and file_size > 0:
+                        _copyfileobj_readinto(fsrc, fdst, min(file_size, COPY_BUFSIZE))
+                        return dst
+
+                    copyfileobj(fsrc, fdst)
+
+            # Issue 43219, raise a less confusing exception
+            except IsADirectoryError as e:
+                if not os.path.exists(dst):
+                    raise FileNotFoundError(f'Directory does not exist: {dst}') from e
+                else:
+                    raise
+
+    return dst
+
+def copymode(src, dst, *, follow_symlinks=True):
+    """Copy mode bits from src to dst.
+
+    If follow_symlinks is not set, symlinks aren't followed if and only
+    if both `src` and `dst` are symlinks.  If `lchmod` isn't available
+    (e.g. Linux) this method does nothing.
+
+    """
+    sys.audit("shutil.copymode", src, dst)
+
+    if not follow_symlinks and _islink(src) and os.path.islink(dst):
+        if hasattr(os, 'lchmod'):
+            stat_func, chmod_func = os.lstat, os.lchmod
+        else:
+            return
+    else:
+        stat_func, chmod_func = _stat, os.chmod
+
+    st = stat_func(src)
+    chmod_func(dst, stat.S_IMODE(st.st_mode))
+
+if hasattr(os, 'listxattr'):
+    def _copyxattr(src, dst, *, follow_symlinks=True):
+        """Copy extended filesystem attributes from `src` to `dst`.
+
+        Overwrite existing attributes.
+
+        If `follow_symlinks` is false, symlinks won't be followed.
+
+        """
+
+        try:
+            names = os.listxattr(src, follow_symlinks=follow_symlinks)
+        except OSError as e:
+            if e.errno not in (errno.ENOTSUP, errno.ENODATA, errno.EINVAL):
+                raise
+            return
+        for name in names:
+            try:
+                value = os.getxattr(src, name, follow_symlinks=follow_symlinks)
+                os.setxattr(dst, name, value, follow_symlinks=follow_symlinks)
+            except OSError as e:
+                if e.errno not in (errno.EPERM, errno.ENOTSUP, errno.ENODATA,
+                                   errno.EINVAL):
+                    raise
+else:
+    def _copyxattr(*args, **kwargs):
+        pass
+
+def copystat(src, dst, *, follow_symlinks=True):
+    """Copy file metadata
+
+    Copy the permission bits, last access time, last modification time, and
+    flags from `src` to `dst`. On Linux, copystat() also copies the "extended
+    attributes" where possible. The file contents, owner, and group are
+    unaffected. `src` and `dst` are path-like objects or path names given as
+    strings.
+
+    If the optional flag `follow_symlinks` is not set, symlinks aren't
+    followed if and only if both `src` and `dst` are symlinks.
+    """
+    sys.audit("shutil.copystat", src, dst)
+
+    def _nop(*args, ns=None, follow_symlinks=None):
+        pass
+
+    # follow symlinks (aka don't not follow symlinks)
+    follow = follow_symlinks or not (_islink(src) and os.path.islink(dst))
+    if follow:
+        # use the real function if it exists
+        def lookup(name):
+            return getattr(os, name, _nop)
+    else:
+        # use the real function only if it exists
+        # *and* it supports follow_symlinks
+        def lookup(name):
+            fn = getattr(os, name, _nop)
+            if fn in os.supports_follow_symlinks:
+                return fn
+            return _nop
+
+    if isinstance(src, os.DirEntry):
+        st = src.stat(follow_symlinks=follow)
+    else:
+        st = lookup("stat")(src, follow_symlinks=follow)
+    mode = stat.S_IMODE(st.st_mode)
+    lookup("utime")(dst, ns=(st.st_atime_ns, st.st_mtime_ns),
+        follow_symlinks=follow)
+    # We must copy extended attributes before the file is (potentially)
+    # chmod()'ed read-only, otherwise setxattr() will error with -EACCES.
+    _copyxattr(src, dst, follow_symlinks=follow)
+    try:
+        lookup("chmod")(dst, mode, follow_symlinks=follow)
+    except NotImplementedError:
+        # if we got a NotImplementedError, it's because
+        #   * follow_symlinks=False,
+        #   * lchown() is unavailable, and
+        #   * either
+        #       * fchownat() is unavailable or
+        #       * fchownat() doesn't implement AT_SYMLINK_NOFOLLOW.
+        #         (it returned ENOSUP.)
+        # therefore we're out of options--we simply cannot chown the
+        # symlink.  give up, suppress the error.
+        # (which is what shutil always did in this circumstance.)
+        pass
+    if hasattr(st, 'st_flags'):
+        try:
+            lookup("chflags")(dst, st.st_flags, follow_symlinks=follow)
+        except OSError as why:
+            for err in 'EOPNOTSUPP', 'ENOTSUP':
+                if hasattr(errno, err) and why.errno == getattr(errno, err):
+                    break
+            else:
+                raise
+
+def copy(src, dst, *, follow_symlinks=True):
+    """Copy data and mode bits ("cp src dst"). Return the file's destination.
+
+    The destination may be a directory.
+
+    If follow_symlinks is false, symlinks won't be followed. This
+    resembles GNU's "cp -P src dst".
+
+    If source and destination are the same file, a SameFileError will be
+    raised.
+
+    """
+    if os.path.isdir(dst):
+        dst = os.path.join(dst, os.path.basename(src))
+    copyfile(src, dst, follow_symlinks=follow_symlinks)
+    copymode(src, dst, follow_symlinks=follow_symlinks)
+    return dst
+
+def copy2(src, dst, *, follow_symlinks=True):
+    """Copy data and metadata. Return the file's destination.
+
+    Metadata is copied with copystat(). Please see the copystat function
+    for more information.
+
+    The destination may be a directory.
+
+    If follow_symlinks is false, symlinks won't be followed. This
+    resembles GNU's "cp -P src dst".
+    """
+    if os.path.isdir(dst):
+        dst = os.path.join(dst, os.path.basename(src))
+    copyfile(src, dst, follow_symlinks=follow_symlinks)
+    copystat(src, dst, follow_symlinks=follow_symlinks)
+    return dst
+
+def ignore_patterns(*patterns):
+    """Function that can be used as copytree() ignore parameter.
+
+    Patterns is a sequence of glob-style patterns
+    that are used to exclude files"""
+    def _ignore_patterns(path, names):
+        ignored_names = []
+        for pattern in patterns:
+            ignored_names.extend(fnmatch.filter(names, pattern))
+        return set(ignored_names)
+    return _ignore_patterns
+
+def _copytree(entries, src, dst, symlinks, ignore, copy_function,
+              ignore_dangling_symlinks, dirs_exist_ok=False):
+    if ignore is not None:
+        ignored_names = ignore(os.fspath(src), [x.name for x in entries])
+    else:
+        ignored_names = set()
+
+    os.makedirs(dst, exist_ok=dirs_exist_ok)
+    errors = []
+    use_srcentry = copy_function is copy2 or copy_function is copy
+
+    for srcentry in entries:
+        if srcentry.name in ignored_names:
+            continue
+        srcname = os.path.join(src, srcentry.name)
+        dstname = os.path.join(dst, srcentry.name)
+        srcobj = srcentry if use_srcentry else srcname
+        try:
+            is_symlink = srcentry.is_symlink()
+            if is_symlink and os.name == 'nt':
+                # Special check for directory junctions, which appear as
+                # symlinks but we want to recurse.
+                lstat = srcentry.stat(follow_symlinks=False)
+                if lstat.st_reparse_tag == stat.IO_REPARSE_TAG_MOUNT_POINT:
+                    is_symlink = False
+            if is_symlink:
+                linkto = os.readlink(srcname)
+                if symlinks:
+                    # We can't just leave it to `copy_function` because legacy
+                    # code with a custom `copy_function` may rely on copytree
+                    # doing the right thing.
+                    os.symlink(linkto, dstname)
+                    copystat(srcobj, dstname, follow_symlinks=not symlinks)
+                else:
+                    # ignore dangling symlink if the flag is on
+                    if not os.path.exists(linkto) and ignore_dangling_symlinks:
+                        continue
+                    # otherwise let the copy occur. copy2 will raise an error
+                    if srcentry.is_dir():
+                        copytree(srcobj, dstname, symlinks, ignore,
+                                 copy_function, dirs_exist_ok=dirs_exist_ok)
+                    else:
+                        copy_function(srcobj, dstname)
+            elif srcentry.is_dir():
+                copytree(srcobj, dstname, symlinks, ignore, copy_function,
+                         dirs_exist_ok=dirs_exist_ok)
+            else:
+                # Will raise a SpecialFileError for unsupported file types
+                copy_function(srcobj, dstname)
+        # catch the Error from the recursive copytree so that we can
+        # continue with other files
+        except Error as err:
+            errors.extend(err.args[0])
+        except OSError as why:
+            errors.append((srcname, dstname, str(why)))
+    try:
+        copystat(src, dst)
+    except OSError as why:
+        # Copying file access times may fail on Windows
+        if getattr(why, 'winerror', None) is None:
+            errors.append((src, dst, str(why)))
+    if errors:
+        raise Error(errors)
+    return dst
+
+def copytree(src, dst, symlinks=False, ignore=None, copy_function=copy2,
+             ignore_dangling_symlinks=False, dirs_exist_ok=False):
+    """Recursively copy a directory tree and return the destination directory.
+
+    dirs_exist_ok dictates whether to raise an exception in case dst or any
+    missing parent directory already exists.
+
+    If exception(s) occur, an Error is raised with a list of reasons.
+
+    If the optional symlinks flag is true, symbolic links in the
+    source tree result in symbolic links in the destination tree; if
+    it is false, the contents of the files pointed to by symbolic
+    links are copied. If the file pointed by the symlink doesn't
+    exist, an exception will be added in the list of errors raised in
+    an Error exception at the end of the copy process.
+
+    You can set the optional ignore_dangling_symlinks flag to true if you
+    want to silence this exception. Notice that this has no effect on
+    platforms that don't support os.symlink.
+
+    The optional ignore argument is a callable. If given, it
+    is called with the `src` parameter, which is the directory
+    being visited by copytree(), and `names` which is the list of
+    `src` contents, as returned by os.listdir():
+
+        callable(src, names) -> ignored_names
+
+    Since copytree() is called recursively, the callable will be
+    called once for each directory that is copied. It returns a
+    list of names relative to the `src` directory that should
+    not be copied.
+
+    The optional copy_function argument is a callable that will be used
+    to copy each file. It will be called with the source path and the
+    destination path as arguments. By default, copy2() is used, but any
+    function that supports the same signature (like copy()) can be used.
+
+    """
+    sys.audit("shutil.copytree", src, dst)
+    with os.scandir(src) as itr:
+        entries = list(itr)
+    return _copytree(entries=entries, src=src, dst=dst, symlinks=symlinks,
+                     ignore=ignore, copy_function=copy_function,
+                     ignore_dangling_symlinks=ignore_dangling_symlinks,
+                     dirs_exist_ok=dirs_exist_ok)
+
+if hasattr(os.stat_result, 'st_file_attributes'):
+    # Special handling for directory junctions to make them behave like
+    # symlinks for shutil.rmtree, since in general they do not appear as
+    # regular links.
+    def _rmtree_isdir(entry):
+        try:
+            st = entry.stat(follow_symlinks=False)
+            return (stat.S_ISDIR(st.st_mode) and not
+                (st.st_file_attributes & stat.FILE_ATTRIBUTE_REPARSE_POINT
+                 and st.st_reparse_tag == stat.IO_REPARSE_TAG_MOUNT_POINT))
+        except OSError:
+            return False
+
+    def _rmtree_islink(path):
+        try:
+            st = os.lstat(path)
+            return (stat.S_ISLNK(st.st_mode) or
+                (st.st_file_attributes & stat.FILE_ATTRIBUTE_REPARSE_POINT
+                 and st.st_reparse_tag == stat.IO_REPARSE_TAG_MOUNT_POINT))
+        except OSError:
+            return False
+else:
+    def _rmtree_isdir(entry):
+        try:
+            return entry.is_dir(follow_symlinks=False)
+        except OSError:
+            return False
+
+    def _rmtree_islink(path):
+        return os.path.islink(path)
+
+# version vulnerable to race conditions
+def _rmtree_unsafe(path, onerror):
+    try:
+        with os.scandir(path) as scandir_it:
+            entries = list(scandir_it)
+    except OSError:
+        onerror(os.scandir, path, sys.exc_info())
+        entries = []
+    for entry in entries:
+        fullname = entry.path
+        if _rmtree_isdir(entry):
+            try:
+                if entry.is_symlink():
+                    # This can only happen if someone replaces
+                    # a directory with a symlink after the call to
+                    # os.scandir or entry.is_dir above.
+                    raise OSError("Cannot call rmtree on a symbolic link")
+            except OSError:
+                onerror(os.path.islink, fullname, sys.exc_info())
+                continue
+            _rmtree_unsafe(fullname, onerror)
+        else:
+            try:
+                os.unlink(fullname)
+            except OSError:
+                onerror(os.unlink, fullname, sys.exc_info())
+    try:
+        os.rmdir(path)
+    except OSError:
+        onerror(os.rmdir, path, sys.exc_info())
+
+# Version using fd-based APIs to protect against races
+def _rmtree_safe_fd(topfd, path, onerror):
+    try:
+        with os.scandir(topfd) as scandir_it:
+            entries = list(scandir_it)
+    except OSError as err:
+        err.filename = path
+        onerror(os.scandir, path, sys.exc_info())
+        return
+    for entry in entries:
+        fullname = os.path.join(path, entry.name)
+        try:
+            is_dir = entry.is_dir(follow_symlinks=False)
+        except OSError:
+            is_dir = False
+        else:
+            if is_dir:
+                try:
+                    orig_st = entry.stat(follow_symlinks=False)
+                    is_dir = stat.S_ISDIR(orig_st.st_mode)
+                except OSError:
+                    onerror(os.lstat, fullname, sys.exc_info())
+                    continue
+        if is_dir:
+            try:
+                dirfd = os.open(entry.name, os.O_RDONLY, dir_fd=topfd)
+            except OSError:
+                onerror(os.open, fullname, sys.exc_info())
+            else:
+                try:
+                    if os.path.samestat(orig_st, os.fstat(dirfd)):
+                        _rmtree_safe_fd(dirfd, fullname, onerror)
+                        try:
+                            os.rmdir(entry.name, dir_fd=topfd)
+                        except OSError:
+                            onerror(os.rmdir, fullname, sys.exc_info())
+                    else:
+                        try:
+                            # This can only happen if someone replaces
+                            # a directory with a symlink after the call to
+                            # os.scandir or stat.S_ISDIR above.
+                            raise OSError("Cannot call rmtree on a symbolic "
+                                          "link")
+                        except OSError:
+                            onerror(os.path.islink, fullname, sys.exc_info())
+                finally:
+                    os.close(dirfd)
+        else:
+            try:
+                os.unlink(entry.name, dir_fd=topfd)
+            except OSError:
+                onerror(os.unlink, fullname, sys.exc_info())
+
+_use_fd_functions = ({os.open, os.stat, os.unlink, os.rmdir} <=
+                     os.supports_dir_fd and
+                     os.scandir in os.supports_fd and
+                     os.stat in os.supports_follow_symlinks)
+
+def rmtree(path, ignore_errors=False, onerror=None):
+    """Recursively delete a directory tree.
+
+    If ignore_errors is set, errors are ignored; otherwise, if onerror
+    is set, it is called to handle the error with arguments (func,
+    path, exc_info) where func is platform and implementation dependent;
+    path is the argument to that function that caused it to fail; and
+    exc_info is a tuple returned by sys.exc_info().  If ignore_errors
+    is false and onerror is None, an exception is raised.
+
+    """
+    sys.audit("shutil.rmtree", path)
+    if ignore_errors:
+        def onerror(*args):
+            pass
+    elif onerror is None:
+        def onerror(*args):
+            raise
+    if _use_fd_functions:
+        # While the unsafe rmtree works fine on bytes, the fd based does not.
+        if isinstance(path, bytes):
+            path = os.fsdecode(path)
+        # Note: To guard against symlink races, we use the standard
+        # lstat()/open()/fstat() trick.
+        try:
+            orig_st = os.lstat(path)
+        except Exception:
+            onerror(os.lstat, path, sys.exc_info())
+            return
+        try:
+            fd = os.open(path, os.O_RDONLY)
+        except Exception:
+            onerror(os.open, path, sys.exc_info())
+            return
+        try:
+            if os.path.samestat(orig_st, os.fstat(fd)):
+                _rmtree_safe_fd(fd, path, onerror)
+                try:
+                    os.rmdir(path)
+                except OSError:
+                    onerror(os.rmdir, path, sys.exc_info())
+            else:
+                try:
+                    # symlinks to directories are forbidden, see bug #1669
+                    raise OSError("Cannot call rmtree on a symbolic link")
+                except OSError:
+                    onerror(os.path.islink, path, sys.exc_info())
+        finally:
+            os.close(fd)
+    else:
+        try:
+            if _rmtree_islink(path):
+                # symlinks to directories are forbidden, see bug #1669
+                raise OSError("Cannot call rmtree on a symbolic link")
+        except OSError:
+            onerror(os.path.islink, path, sys.exc_info())
+            # can't continue even if onerror hook returns
+            return
+        return _rmtree_unsafe(path, onerror)
+
+# Allow introspection of whether or not the hardening against symlink
+# attacks is supported on the current platform
+rmtree.avoids_symlink_attacks = _use_fd_functions
+
+def _basename(path):
+    """A basename() variant which first strips the trailing slash, if present.
+    Thus we always get the last component of the path, even for directories.
+
+    path: Union[PathLike, str]
+
+    e.g.
+    >>> os.path.basename('/bar/foo')
+    'foo'
+    >>> os.path.basename('/bar/foo/')
+    ''
+    >>> _basename('/bar/foo/')
+    'foo'
+    """
+    path = os.fspath(path)
+    sep = os.path.sep + (os.path.altsep or '')
+    return os.path.basename(path.rstrip(sep))
+
+def move(src, dst, copy_function=copy2):
+    """Recursively move a file or directory to another location. This is
+    similar to the Unix "mv" command. Return the file or directory's
+    destination.
+
+    If the destination is a directory or a symlink to a directory, the source
+    is moved inside the directory. The destination path must not already
+    exist.
+
+    If the destination already exists but is not a directory, it may be
+    overwritten depending on os.rename() semantics.
+
+    If the destination is on our current filesystem, then rename() is used.
+    Otherwise, src is copied to the destination and then removed. Symlinks are
+    recreated under the new name if os.rename() fails because of cross
+    filesystem renames.
+
+    The optional `copy_function` argument is a callable that will be used
+    to copy the source or it will be delegated to `copytree`.
+    By default, copy2() is used, but any function that supports the same
+    signature (like copy()) can be used.
+
+    A lot more could be done here...  A look at a mv.c shows a lot of
+    the issues this implementation glosses over.
+
+    """
+    sys.audit("shutil.move", src, dst)
+    real_dst = dst
+    if os.path.isdir(dst):
+        if _samefile(src, dst):
+            # We might be on a case insensitive filesystem,
+            # perform the rename anyway.
+            os.rename(src, dst)
+            return
+
+        # Using _basename instead of os.path.basename is important, as we must
+        # ignore any trailing slash to avoid the basename returning ''
+        real_dst = os.path.join(dst, _basename(src))
+
+        if os.path.exists(real_dst):
+            raise Error("Destination path '%s' already exists" % real_dst)
+    try:
+        os.rename(src, real_dst)
+    except OSError:
+        if os.path.islink(src):
+            linkto = os.readlink(src)
+            os.symlink(linkto, real_dst)
+            os.unlink(src)
+        elif os.path.isdir(src):
+            if _destinsrc(src, dst):
+                raise Error("Cannot move a directory '%s' into itself"
+                            " '%s'." % (src, dst))
+            if (_is_immutable(src)
+                    or (not os.access(src, os.W_OK) and os.listdir(src)
+                        and sys.platform == 'darwin')):
+                raise PermissionError("Cannot move the non-empty directory "
+                                      "'%s': Lacking write permission to '%s'."
+                                      % (src, src))
+            copytree(src, real_dst, copy_function=copy_function,
+                     symlinks=True)
+            rmtree(src)
+        else:
+            copy_function(src, real_dst)
+            os.unlink(src)
+    return real_dst
+
+def _destinsrc(src, dst):
+    src = os.path.abspath(src)
+    dst = os.path.abspath(dst)
+    if not src.endswith(os.path.sep):
+        src += os.path.sep
+    if not dst.endswith(os.path.sep):
+        dst += os.path.sep
+    return dst.startswith(src)
+
+def _is_immutable(src):
+    st = _stat(src)
+    immutable_states = [stat.UF_IMMUTABLE, stat.SF_IMMUTABLE]
+    return hasattr(st, 'st_flags') and st.st_flags in immutable_states
+
+def _get_gid(name):
+    """Returns a gid, given a group name."""
+    if getgrnam is None or name is None:
+        return None
+    try:
+        result = getgrnam(name)
+    except KeyError:
+        result = None
+    if result is not None:
+        return result[2]
+    return None
+
+def _get_uid(name):
+    """Returns an uid, given a user name."""
+    if getpwnam is None or name is None:
+        return None
+    try:
+        result = getpwnam(name)
+    except KeyError:
+        result = None
+    if result is not None:
+        return result[2]
+    return None
+
+def _make_tarball(base_name, base_dir, compress="gzip", verbose=0, dry_run=0,
+                  owner=None, group=None, logger=None):
+    """Create a (possibly compressed) tar file from all the files under
+    'base_dir'.
+
+    'compress' must be "gzip" (the default), "bzip2", "xz", or None.
+
+    'owner' and 'group' can be used to define an owner and a group for the
+    archive that is being built. If not provided, the current owner and group
+    will be used.
+
+    The output tar file will be named 'base_name' +  ".tar", possibly plus
+    the appropriate compression extension (".gz", ".bz2", or ".xz").
+
+    Returns the output filename.
+    """
+    if compress is None:
+        tar_compression = ''
+    elif _ZLIB_SUPPORTED and compress == 'gzip':
+        tar_compression = 'gz'
+    elif _BZ2_SUPPORTED and compress == 'bzip2':
+        tar_compression = 'bz2'
+    elif _LZMA_SUPPORTED and compress == 'xz':
+        tar_compression = 'xz'
+    else:
+        raise ValueError("bad value for 'compress', or compression format not "
+                         "supported : {0}".format(compress))
+
+    import tarfile  # late import for breaking circular dependency
+
+    compress_ext = '.' + tar_compression if compress else ''
+    archive_name = base_name + '.tar' + compress_ext
+    archive_dir = os.path.dirname(archive_name)
+
+    if archive_dir and not os.path.exists(archive_dir):
+        if logger is not None:
+            logger.info("creating %s", archive_dir)
+        if not dry_run:
+            os.makedirs(archive_dir)
+
+    # creating the tarball
+    if logger is not None:
+        logger.info('Creating tar archive')
+
+    uid = _get_uid(owner)
+    gid = _get_gid(group)
+
+    def _set_uid_gid(tarinfo):
+        if gid is not None:
+            tarinfo.gid = gid
+            tarinfo.gname = group
+        if uid is not None:
+            tarinfo.uid = uid
+            tarinfo.uname = owner
+        return tarinfo
+
+    if not dry_run:
+        tar = tarfile.open(archive_name, 'w|%s' % tar_compression)
+        try:
+            tar.add(base_dir, filter=_set_uid_gid)
+        finally:
+            tar.close()
+
+    return archive_name
+
+def _make_zipfile(base_name, base_dir, verbose=0, dry_run=0, logger=None):
+    """Create a zip file from all the files under 'base_dir'.
+
+    The output zip file will be named 'base_name' + ".zip".  Returns the
+    name of the output zip file.
+    """
+    import zipfile  # late import for breaking circular dependency
+
+    zip_filename = base_name + ".zip"
+    archive_dir = os.path.dirname(base_name)
+
+    if archive_dir and not os.path.exists(archive_dir):
+        if logger is not None:
+            logger.info("creating %s", archive_dir)
+        if not dry_run:
+            os.makedirs(archive_dir)
+
+    if logger is not None:
+        logger.info("creating '%s' and adding '%s' to it",
+                    zip_filename, base_dir)
+
+    if not dry_run:
+        with zipfile.ZipFile(zip_filename, "w",
+                             compression=zipfile.ZIP_DEFLATED) as zf:
+            path = os.path.normpath(base_dir)
+            if path != os.curdir:
+                zf.write(path, path)
+                if logger is not None:
+                    logger.info("adding '%s'", path)
+            for dirpath, dirnames, filenames in os.walk(base_dir):
+                for name in sorted(dirnames):
+                    path = os.path.normpath(os.path.join(dirpath, name))
+                    zf.write(path, path)
+                    if logger is not None:
+                        logger.info("adding '%s'", path)
+                for name in filenames:
+                    path = os.path.normpath(os.path.join(dirpath, name))
+                    if os.path.isfile(path):
+                        zf.write(path, path)
+                        if logger is not None:
+                            logger.info("adding '%s'", path)
+
+    return zip_filename
+
+_ARCHIVE_FORMATS = {
+    'tar':   (_make_tarball, [('compress', None)], "uncompressed tar file"),
+}
+
+if _ZLIB_SUPPORTED:
+    _ARCHIVE_FORMATS['gztar'] = (_make_tarball, [('compress', 'gzip')],
+                                "gzip'ed tar-file")
+    _ARCHIVE_FORMATS['zip'] = (_make_zipfile, [], "ZIP file")
+
+if _BZ2_SUPPORTED:
+    _ARCHIVE_FORMATS['bztar'] = (_make_tarball, [('compress', 'bzip2')],
+                                "bzip2'ed tar-file")
+
+if _LZMA_SUPPORTED:
+    _ARCHIVE_FORMATS['xztar'] = (_make_tarball, [('compress', 'xz')],
+                                "xz'ed tar-file")
+
+def get_archive_formats():
+    """Returns a list of supported formats for archiving and unarchiving.
+
+    Each element of the returned sequence is a tuple (name, description)
+    """
+    formats = [(name, registry[2]) for name, registry in
+               _ARCHIVE_FORMATS.items()]
+    formats.sort()
+    return formats
+
+def register_archive_format(name, function, extra_args=None, description=''):
+    """Registers an archive format.
+
+    name is the name of the format. function is the callable that will be
+    used to create archives. If provided, extra_args is a sequence of
+    (name, value) tuples that will be passed as arguments to the callable.
+    description can be provided to describe the format, and will be returned
+    by the get_archive_formats() function.
+    """
+    if extra_args is None:
+        extra_args = []
+    if not callable(function):
+        raise TypeError('The %s object is not callable' % function)
+    if not isinstance(extra_args, (tuple, list)):
+        raise TypeError('extra_args needs to be a sequence')
+    for element in extra_args:
+        if not isinstance(element, (tuple, list)) or len(element) !=2:
+            raise TypeError('extra_args elements are : (arg_name, value)')
+
+    _ARCHIVE_FORMATS[name] = (function, extra_args, description)
+
+def unregister_archive_format(name):
+    del _ARCHIVE_FORMATS[name]
+
+def make_archive(base_name, format, root_dir=None, base_dir=None, verbose=0,
+                 dry_run=0, owner=None, group=None, logger=None):
+    """Create an archive file (eg. zip or tar).
+
+    'base_name' is the name of the file to create, minus any format-specific
+    extension; 'format' is the archive format: one of "zip", "tar", "gztar",
+    "bztar", or "xztar".  Or any other registered format.
+
+    'root_dir' is a directory that will be the root directory of the
+    archive; ie. we typically chdir into 'root_dir' before creating the
+    archive.  'base_dir' is the directory where we start archiving from;
+    ie. 'base_dir' will be the common prefix of all files and
+    directories in the archive.  'root_dir' and 'base_dir' both default
+    to the current directory.  Returns the name of the archive file.
+
+    'owner' and 'group' are used when creating a tar archive. By default,
+    uses the current owner and group.
+    """
+    sys.audit("shutil.make_archive", base_name, format, root_dir, base_dir)
+    save_cwd = os.getcwd()
+    if root_dir is not None:
+        if logger is not None:
+            logger.debug("changing into '%s'", root_dir)
+        base_name = os.path.abspath(base_name)
+        if not dry_run:
+            os.chdir(root_dir)
+
+    if base_dir is None:
+        base_dir = os.curdir
+
+    kwargs = {'dry_run': dry_run, 'logger': logger}
+
+    try:
+        format_info = _ARCHIVE_FORMATS[format]
+    except KeyError:
+        raise ValueError("unknown archive format '%s'" % format) from None
+
+    func = format_info[0]
+    for arg, val in format_info[1]:
+        kwargs[arg] = val
+
+    if format != 'zip':
+        kwargs['owner'] = owner
+        kwargs['group'] = group
+
+    try:
+        filename = func(base_name, base_dir, **kwargs)
+    finally:
+        if root_dir is not None:
+            if logger is not None:
+                logger.debug("changing back to '%s'", save_cwd)
+            os.chdir(save_cwd)
+
+    return filename
+
+
+def get_unpack_formats():
+    """Returns a list of supported formats for unpacking.
+
+    Each element of the returned sequence is a tuple
+    (name, extensions, description)
+    """
+    formats = [(name, info[0], info[3]) for name, info in
+               _UNPACK_FORMATS.items()]
+    formats.sort()
+    return formats
+
+def _check_unpack_options(extensions, function, extra_args):
+    """Checks what gets registered as an unpacker."""
+    # first make sure no other unpacker is registered for this extension
+    existing_extensions = {}
+    for name, info in _UNPACK_FORMATS.items():
+        for ext in info[0]:
+            existing_extensions[ext] = name
+
+    for extension in extensions:
+        if extension in existing_extensions:
+            msg = '%s is already registered for "%s"'
+            raise RegistryError(msg % (extension,
+                                       existing_extensions[extension]))
+
+    if not callable(function):
+        raise TypeError('The registered function must be a callable')
+
+
+def register_unpack_format(name, extensions, function, extra_args=None,
+                           description=''):
+    """Registers an unpack format.
+
+    `name` is the name of the format. `extensions` is a list of extensions
+    corresponding to the format.
+
+    `function` is the callable that will be
+    used to unpack archives. The callable will receive archives to unpack.
+    If it's unable to handle an archive, it needs to raise a ReadError
+    exception.
+
+    If provided, `extra_args` is a sequence of
+    (name, value) tuples that will be passed as arguments to the callable.
+    description can be provided to describe the format, and will be returned
+    by the get_unpack_formats() function.
+    """
+    if extra_args is None:
+        extra_args = []
+    _check_unpack_options(extensions, function, extra_args)
+    _UNPACK_FORMATS[name] = extensions, function, extra_args, description
+
+def unregister_unpack_format(name):
+    """Removes the pack format from the registry."""
+    del _UNPACK_FORMATS[name]
+
+def _ensure_directory(path):
+    """Ensure that the parent directory of `path` exists"""
+    dirname = os.path.dirname(path)
+    if not os.path.isdir(dirname):
+        os.makedirs(dirname)
+
+def _unpack_zipfile(filename, extract_dir):
+    """Unpack zip `filename` to `extract_dir`
+    """
+    import zipfile  # late import for breaking circular dependency
+
+    if not zipfile.is_zipfile(filename):
+        raise ReadError("%s is not a zip file" % filename)
+
+    zip = zipfile.ZipFile(filename)
+    try:
+        for info in zip.infolist():
+            name = info.filename
+
+            # don't extract absolute paths or ones with .. in them
+            if name.startswith('/') or '..' in name:
+                continue
+
+            targetpath = os.path.join(extract_dir, *name.split('/'))
+            if not targetpath:
+                continue
+
+            _ensure_directory(targetpath)
+            if not name.endswith('/'):
+                # file
+                with zip.open(name, 'r') as source, \
+                        open(targetpath, 'wb') as target:
+                    copyfileobj(source, target)
+    finally:
+        zip.close()
+
+def _unpack_tarfile(filename, extract_dir):
+    """Unpack tar/tar.gz/tar.bz2/tar.xz `filename` to `extract_dir`
+    """
+    import tarfile  # late import for breaking circular dependency
+    try:
+        tarobj = tarfile.open(filename)
+    except tarfile.TarError:
+        raise ReadError(
+            "%s is not a compressed or uncompressed tar file" % filename)
+    try:
+        tarobj.extractall(extract_dir)
+    finally:
+        tarobj.close()
+
+_UNPACK_FORMATS = {
+    'tar':   (['.tar'], _unpack_tarfile, [], "uncompressed tar file"),
+    'zip':   (['.zip'], _unpack_zipfile, [], "ZIP file"),
+}
+
+if _ZLIB_SUPPORTED:
+    _UNPACK_FORMATS['gztar'] = (['.tar.gz', '.tgz'], _unpack_tarfile, [],
+                                "gzip'ed tar-file")
+
+if _BZ2_SUPPORTED:
+    _UNPACK_FORMATS['bztar'] = (['.tar.bz2', '.tbz2'], _unpack_tarfile, [],
+                                "bzip2'ed tar-file")
+
+if _LZMA_SUPPORTED:
+    _UNPACK_FORMATS['xztar'] = (['.tar.xz', '.txz'], _unpack_tarfile, [],
+                                "xz'ed tar-file")
+
+def _find_unpack_format(filename):
+    for name, info in _UNPACK_FORMATS.items():
+        for extension in info[0]:
+            if filename.endswith(extension):
+                return name
+    return None
+
+def unpack_archive(filename, extract_dir=None, format=None):
+    """Unpack an archive.
+
+    `filename` is the name of the archive.
+
+    `extract_dir` is the name of the target directory, where the archive
+    is unpacked. If not provided, the current working directory is used.
+
+    `format` is the archive format: one of "zip", "tar", "gztar", "bztar",
+    or "xztar".  Or any other registered format.  If not provided,
+    unpack_archive will use the filename extension and see if an unpacker
+    was registered for that extension.
+
+    In case none is found, a ValueError is raised.
+    """
+    sys.audit("shutil.unpack_archive", filename, extract_dir, format)
+
+    if extract_dir is None:
+        extract_dir = os.getcwd()
+
+    extract_dir = os.fspath(extract_dir)
+    filename = os.fspath(filename)
+
+    if format is not None:
+        try:
+            format_info = _UNPACK_FORMATS[format]
+        except KeyError:
+            raise ValueError("Unknown unpack format '{0}'".format(format)) from None
+
+        func = format_info[1]
+        func(filename, extract_dir, **dict(format_info[2]))
+    else:
+        # we need to look at the registered unpackers supported extensions
+        format = _find_unpack_format(filename)
+        if format is None:
+            raise ReadError("Unknown archive format '{0}'".format(filename))
+
+        func = _UNPACK_FORMATS[format][1]
+        kwargs = dict(_UNPACK_FORMATS[format][2])
+        func(filename, extract_dir, **kwargs)
+
+
+if hasattr(os, 'statvfs'):
+
+    __all__.append('disk_usage')
+    _ntuple_diskusage = collections.namedtuple('usage', 'total used free')
+    _ntuple_diskusage.total.__doc__ = 'Total space in bytes'
+    _ntuple_diskusage.used.__doc__ = 'Used space in bytes'
+    _ntuple_diskusage.free.__doc__ = 'Free space in bytes'
+
+    def disk_usage(path):
+        """Return disk usage statistics about the given path.
+
+        Returned value is a named tuple with attributes 'total', 'used' and
+        'free', which are the amount of total, used and free space, in bytes.
+        """
+        st = os.statvfs(path)
+        free = st.f_bavail * st.f_frsize
+        total = st.f_blocks * st.f_frsize
+        used = (st.f_blocks - st.f_bfree) * st.f_frsize
+        return _ntuple_diskusage(total, used, free)
+
+elif _WINDOWS:
+
+    __all__.append('disk_usage')
+    _ntuple_diskusage = collections.namedtuple('usage', 'total used free')
+
+    def disk_usage(path):
+        """Return disk usage statistics about the given path.
+
+        Returned values is a named tuple with attributes 'total', 'used' and
+        'free', which are the amount of total, used and free space, in bytes.
+        """
+        total, free = nt._getdiskusage(path)
+        used = total - free
+        return _ntuple_diskusage(total, used, free)
+
+
+def chown(path, user=None, group=None):
+    """Change owner user and group of the given path.
+
+    user and group can be the uid/gid or the user/group names, and in that case,
+    they are converted to their respective uid/gid.
+    """
+    sys.audit('shutil.chown', path, user, group)
+
+    if user is None and group is None:
+        raise ValueError("user and/or group must be set")
+
+    _user = user
+    _group = group
+
+    # -1 means don't change it
+    if user is None:
+        _user = -1
+    # user can either be an int (the uid) or a string (the system username)
+    elif isinstance(user, str):
+        _user = _get_uid(user)
+        if _user is None:
+            raise LookupError("no such user: {!r}".format(user))
+
+    if group is None:
+        _group = -1
+    elif not isinstance(group, int):
+        _group = _get_gid(group)
+        if _group is None:
+            raise LookupError("no such group: {!r}".format(group))
+
+    os.chown(path, _user, _group)
+
+def get_terminal_size(fallback=(80, 24)):
+    """Get the size of the terminal window.
+
+    For each of the two dimensions, the environment variable, COLUMNS
+    and LINES respectively, is checked. If the variable is defined and
+    the value is a positive integer, it is used.
+
+    When COLUMNS or LINES is not defined, which is the common case,
+    the terminal connected to sys.__stdout__ is queried
+    by invoking os.get_terminal_size.
+
+    If the terminal size cannot be successfully queried, either because
+    the system doesn't support querying, or because we are not
+    connected to a terminal, the value given in fallback parameter
+    is used. Fallback defaults to (80, 24) which is the default
+    size used by many terminal emulators.
+
+    The value returned is a named tuple of type os.terminal_size.
+    """
+    # columns, lines are the working values
+    try:
+        columns = int(os.environ['COLUMNS'])
+    except (KeyError, ValueError):
+        columns = 0
+
+    try:
+        lines = int(os.environ['LINES'])
+    except (KeyError, ValueError):
+        lines = 0
+
+    # only query if necessary
+    if columns <= 0 or lines <= 0:
+        try:
+            size = os.get_terminal_size(sys.__stdout__.fileno())
+        except (AttributeError, ValueError, OSError):
+            # stdout is None, closed, detached, or not a terminal, or
+            # os.get_terminal_size() is unsupported
+            size = os.terminal_size(fallback)
+        if columns <= 0:
+            columns = size.columns
+        if lines <= 0:
+            lines = size.lines
+
+    return os.terminal_size((columns, lines))
+
+
+# Check that a given file can be accessed with the correct mode.
+# Additionally check that `file` is not a directory, as on Windows
+# directories pass the os.access check.
+def _access_check(fn, mode):
+    return (os.path.exists(fn) and os.access(fn, mode)
+            and not os.path.isdir(fn))
+
+
+def which(cmd, mode=os.F_OK | os.X_OK, path=None):
+    """Given a command, mode, and a PATH string, return the path which
+    conforms to the given mode on the PATH, or None if there is no such
+    file.
+
+    `mode` defaults to os.F_OK | os.X_OK. `path` defaults to the result
+    of os.environ.get("PATH"), or can be overridden with a custom search
+    path.
+
+    """
+    # If we're given a path with a directory part, look it up directly rather
+    # than referring to PATH directories. This includes checking relative to the
+    # current directory, e.g. ./script
+    if os.path.dirname(cmd):
+        if _access_check(cmd, mode):
+            return cmd
+        return None
+
+    use_bytes = isinstance(cmd, bytes)
+
+    if path is None:
+        path = os.environ.get("PATH", None)
+        if path is None:
+            try:
+                path = os.confstr("CS_PATH")
+            except (AttributeError, ValueError):
+                # os.confstr() or CS_PATH is not available
+                path = os.defpath
+        # bpo-35755: Don't use os.defpath if the PATH environment variable is
+        # set to an empty string
+
+    # PATH='' doesn't match, whereas PATH=':' looks in the current directory
+    if not path:
+        return None
+
+    if use_bytes:
+        path = os.fsencode(path)
+        path = path.split(os.fsencode(os.pathsep))
+    else:
+        path = os.fsdecode(path)
+        path = path.split(os.pathsep)
+
+    if sys.platform == "win32":
+        # The current directory takes precedence on Windows.
+        curdir = os.curdir
+        if use_bytes:
+            curdir = os.fsencode(curdir)
+        if curdir not in path:
+            path.insert(0, curdir)
+
+        # PATHEXT is necessary to check on Windows.
+        pathext_source = os.getenv("PATHEXT") or _WIN_DEFAULT_PATHEXT
+        pathext = [ext for ext in pathext_source.split(os.pathsep) if ext]
+
+        if use_bytes:
+            pathext = [os.fsencode(ext) for ext in pathext]
+        # See if the given file matches any of the expected path extensions.
+        # This will allow us to short circuit when given "python.exe".
+        # If it does match, only test that one, otherwise we have to try
+        # others.
+        if any(cmd.lower().endswith(ext.lower()) for ext in pathext):
+            files = [cmd]
+        else:
+            files = [cmd + ext for ext in pathext]
+    else:
+        # On other platforms you don't have things like PATHEXT to tell you
+        # what file suffixes are executable, so just pass on cmd as-is.
+        files = [cmd]
+
+    seen = set()
+    for dir in path:
+        normdir = os.path.normcase(dir)
+        if not normdir in seen:
+            seen.add(normdir)
+            for thefile in files:
+                name = os.path.join(dir, thefile)
+                if _access_check(name, mode):
+                    return name
+    return None