[python-committers] Travis now checks for whitespace issues in PRs

I just pushed a change to master, 3.6, and 3.5 where Tools/scripts/patchcheck.py now has a --travis option which will run the whitespace fixers from make patchcheck but trigger a Travis build failure if any changes were necessary. This only runs on Linux so it is a PR blocker, but also so it isn't done more than once per PR.

This was not backported to 2.7 because I honestly didn't want to do the work to fix the merge conflicts.