Open Stack

Hey all!

https://review.openstack.org/#/c/42178/2 has landed in nova, which means
that nova now requires tox 1.6 or higher (for those folks using tox).
We'll be wanting to port the same change to all of the projects, so if
you use tox for anything, you'll want to go ahead and upgrade.

Why?

Because we landed a patch to tox upstream to use setup.py develop
instead of sdist+install like our run_tests.sh scripts do - this means
that with the new tox config changes, tox runs should be just as quick
as run_tests.sh runs.

Other than speed, it also gets more correctness, as before the process
ran sdist with system python, even if that wasn't the python that was to
be used for the test run.

Enjoy!
Monty