msys2 is broken only on clang, due to -Werror issues in the python
headers as patched by msys2.
MSVC is simply weird... due to the use of an unversioned platlib/purelib
directory, the python2 and python3 components overlap.
Perhaps when this test case was originally created, project tests could
not use a matrix of options? This is certainly possible today, so don't
write special unittest handling for this instead.
This adds proper visibility into what gets run and what doesn't. Now we
know which python executables got tested and which got skipped.
Eli Schwartz