https://github.com/python/core-workflow/issues/3 is tracking adding a check for proper whitespace in PRs as we had that on hg.python.org but we are missing it on GitHub. I have a PR at https://github.com/python/cpython/pull/2367 that I think does the right thing, but I would appreciate a quick review to make sure I didn't miss anything since this will block PRs if I get it wrong. :)