Fix Python build on OS X.
Fix Python build on OS X.

Travis CI doesn't support Python builds on OSX according to:
https://docs.travis-ci.com/user/languages/python/

This fixes the Python build on OS X by using `language: generic` and manually
installing Python on OS X.

mbrukman/cloud-launcher,mbrukman/cloud-launcher,mbrukman/cloud-launcher,mbrukman/cloud-launcher