Looks like they added some new warnings that are causing the docs build to fail (e.g. https://travis-ci.org/python/cpython/jobs/232903226 and https://travis-ci.org/python/cpython/jobs/232897796).

I will see if I have time to fix this before I leave for PyCon US today, but there's no guarantee. If someone has time to fix this then I've opened https://bugs.python.org/issue30380 to track the problem and give my take on a solution.