Suggested by Terry J. Reedy in #12298.

Text adapted from the PEP.  Addition requested by Terry J. Reedy on
2011-02-23 on python-dev.

This was discussed some months ago on python-dev.  Having tons of links
to the definition of True would be annoying, contrary to links to e.g.
the nonlocal or with statements doc.

The right-hand part in [extension: foo] is now used as the name of the
extension module.  (I changed the separator from = to : and allowed
whitespace to make the sections look nicer.)

rstlint complains about packaging docs but I’m working on those in
another patch.

This huge module is the heir of six distutils modules, and contains
a number of miscellaneous functions.  I have attempted to help readers
of the source code with an annoted __all__.  Removed or deprecated
functions have been removed from the documentation; I’m working on
another patch to document the remaining public functions.

For the curious:

The unzip_file and untar_file were used by (or intended to be used by)
“pysetup install path/to/archive.tar.gz”, but the code presently used
shutil.unpack_archive and an helper function, so I just deleted them.
They’re still in the repository if we need them in the future.

The find_packages function is not used anymore but I want to discuss
module and package auto-discovery (in “pysetup create”) again before
removing it.

subst_vars now lives in sysconfig; rfc822_escape is inlined in
packaging.metadata.  Other functions are for internal use only, or
deprecated; I have left them out of __all__ and sprinkled TODO notes
for future cleanups.

Patch by Hallvard B Furuseth.

- Issue #9651: Fix a crash when ctypes.create_string_buffer(0) was passed to file.write()
- Issue #11241: subclasses of ctypes.Array can now be subclassed.

some functions like file.write().

Windows does set the errno attribute to ENOENT, but the error message
displays the Windows error number (3 -> ERROR_PATH_NOT_FOUND), not the
errno number (2 -> ENOENT).
The Unix errno corresponding to 3 is ESRCH, explaining the confusion,
which can be seen in the following snippet:

>>> shutil.rmtree("foo")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "Z:\default\lib\shutil.py", line 272, in rmtree
    onerror(os.listdir, path, sys.exc_info())
  File "Z:\default\lib\shutil.py", line 270, in rmtree
    names = os.listdir(path)
WindowsError: [Error 3] The system cannot find the path specified:
'foo\\*.*'
>>> e = sys.last_value
>>> e.errno
2
>>> e.winerror
3
>>> errno.errorcode[2]
'ENOENT'

For reference, see PC/errmap.h and
http://msdn.microsoft.com/en-us/library/ms681382%28v=vs.85%29.aspx

There was already a test for this, but it was complicated and had a
subtle bug (custom command objects need to be put in dist.command_obj so
that other command objects may see them) that rendered it moot.

Packaging uses the shutil.make_archive function copied from distutils,
which does not support compress.  There is no test to check that
“bdist --format whatever” works, so this slipped by.

These options were used to implement “setup.py --name”,
“setup.py --version”, etc. which are now handled by the pysetup metadata
action or direct parsing of the setup.cfg file.

As a side effect, the Distribution class no longer accepts a 'url' key
in its *attrs* argument: it has to be 'home-page' to be recognized as a
valid metadata field and passed down to the dist.metadata object.

I cleaned up some comments, docstrings and code along the way.