Several test cases in distutils use PyPIRCCommandTestCase as
their base class and as a result of that the following tests
were ran more than once:

* test_server_registration
* test_server_empty_registration
* test_config_interpolation

This commit moves the infrastructure used by other tests
into a new BasePyPIRCCommandTestCase class.

I noticed that there is no test for this feature while doing
triaging work on pypa/pypi-legacy.

Issue #27048: Prevents distutils failing on Windows when environment variables contain non-ASCII characters

Issue #27048: Prevents distutils failing on Windows when environment variables contain non-ASCII characters

   _sysconfigdata module too.

  plat-$(PLATFORM_TRIPLET).
  Rename the config directory (LIBPL) from config-$(LDVERSION) to
  config-$(LDVERSION)-$(PLATFORM_TRIPLET).
  Install the platform specifc _sysconfigdata module into the platform
  directory and rename it to include the ABIFLAGS.

Initial patch by ingrid.

  Patch by Xavier de Gaye.

Initial patch by Claudiu Popa.