Part of the problem with everything being global here is that `auth.py` implicitly knows about the Nova and LB URL structures, rather than having some way of this function having a reference to the Nova and LB mocks to ask them questions.

If you're not going to be doing much with this in the next few days, I could demonstrate what I mean with a plugin PR.  At least, I hope I'll get it done quickly so it'll be very clear what I'm suggesting :).