GitLab

Updated Python versions

MRG: allow choosing the test docker image

Machinery to specify docker image on which to run tests.

MRG: fixes for platform, pypy wheel builds

* pr/301:
  Uncomment code
  Warn and exit when no supported wheels found

MRG: Use packaging; add test for supported wheels

Replace internal pip code with packaging code (thanks @pfmoore).

Add tests for supported_wheels.py script.