The original idea was that we'd have a "python27" job. But it turns out
that "python27" isn't actually as universal as you might think.
"tox-py27" on the other hand is a thing that can and should always work
for people who want to run tox with the py27 env.
Port in the jobs we had in openstack-zuul-jobs.
Also, copy in the text of the old shell scripts so that we can iterate on
them and make them better piecemeal.
These are named zuul-tox not tox because we already have tox jobs
defined elsewhere. We'll need to do the naming dance while we work on