Figured out the answer to my last question while looking into fixing it.  The devguide documents both running tests via regrtest and running them via unittest test discovery.  regrtest works:

  ./python -m test -v distutils.test

But unittest doesn't:
  ./python -m unittest -v test.test_distutils
  ./python -m unittest -v distutils.test.test_file_utils
  # etc

I'll submit a separate PR to get that working.