The AST_H_DIR variable was removed from Makefile.pre.in by the commit
a5c62a8e9f0de6c4133825a5710984a3cd5e102b (bpo-23404).

AST_H_DIR was hardcoded to "Include", so replace the removed variable
by its content.

Remove also ASDLGEN variable from sysconfig example since this
variable was also removed.

BuildExtTestCase of test_distutils now uses support.temp_cwd() in
setUp() to remove files created in the current working in all
BuildExtTestCase unit tests, not only test_build_ext().

Move also tearDown() just after setUp().

test_build_ext() of test_distutils now uses support.temp_cwd() to
prevent the creation of a pdb file in the current working directory
on Windows.

It has been documented as unused since 6c6844a2fa30 (2000-05-25)

Patch by Eric N. Vander Weele.

that is not found

Extract methods from sdist.add_defaults, allowing subclasses to override or inject different behaviors.

We can't just skip the test if docutils is available,
but pygments is not because the purpose of the test
was testing a bug in _check_rst_data().

Patch by Roumen Petrov, based on original patch by Jason Tishler.

Patch by Valerie Lambert.

environment variable that is defined when cross-compiling.

regular expression.  Deprecation warning is emitted if uses them in the
middle of the regular expression.

Why do we have two sysconfig modules again?

And most of the tools.

Patch by Emanual Barry, reviewed by me, Serhiy Storchaka, and
Martin Panter.

Issue #27960: Revert state to 675e20c38fdac6, backing out all changes by developed for Issue #12885.