I think we need this addition in setup.py as well.

That said, setup.py should probably have a test_packages declaration that adds to required_packages, since I don't think we want/need Mock in the setup requirements (but do need it for the setup.py test command)

I hate how non-DRY it is, but not sure how to get around the problem, since the requirements.txt file is for pip and setup.py needs to register it's own list of requirements, which are the same, but a different format.