The attempt at a move to user-name is an exercise in churn, and is
filling everyone's logs with admonitions to change the name of their
variables - which does not work if they do. Swap this, effectively
reverting the attempt at a move. user-name will continue to work on
the off chance anyone started consuming that path, which is unlikely
because none of the consuming programs expose that as an actual option.

Closes-Bug: 1498247

Change-Id: I62d991fda1df63c9cbabfde2f6836bc031f5147c

If the user passes a Session in, we can pull the endpoint to use for
discovery from the Session itself, rather than erroring.

Closes-Bug: #1513839
Co-Authored-By: Dolph Mathews <dolph.mathews@gmail.com>
Change-Id: I82a41c67f80d2494f04739d82b112b7ff1dc4682

abstractmethod bodies aren't going to be called by unit tests, so
there's no way to get coverage. The code in an abstractmethod body
should be marked with "# pragma: no cover" so that they don't show
up as missed in the coverage report.

Change-Id: I88a7481ab22f2ce1abfd62badc5f5048acc6929f

These are all object methods, not independent functions.

Change-Id: I3c232d922e61a94c7dc2c2b9a8d3768fd42be1a7

Although a bare docstring is entirely valid grammar, those new to Python find
that pattern baffling, *especially* when other similar methods contain pass
statements. So, for consistency, add a pass statement to otherwise bare
@abc.abstractmethods.

Note that the implementation of an @abc.abstractmethod (in the abstract
base class) can still be called by concrete children, so suddenly
raising a NotImplementedError() instead might be "surprising" to
implementors. A no-op such as "pass" or "return None" is preferable.

Change-Id: I79969ad1a3429516ea785c649a165ead54944225

Using a mutable type implies that it's acceptable for the set of
publicly-accessible attributes to be mutated at runtime, which defeats
their intended purpose of documenting the public interface. Tuples are
immutable.

Change-Id: Ib3ab93224ba240040b08ece481ef5ba620c3f658

A common case is for Nova (or other service) to create a service
authentication plugin from a configuration file and then have many
greenlet threads that want to reuse that authentication. If a token
expires then many threads all try and fetch a new token to use and can
step over each other.

I was hoping for a way to put a lock in so that all plugins were thread
safe however fixing it for identity plugins solves almost all real world
situations and anyone doing non-identity plugins will have to manage
threads themselves.

Change-Id: Ib6487de7de638abc69660c851bd048a8ec177109
Closes-Bug: #1493835

Iterating over a dict results in the keys.

Using the 'in' operator on a dict checks if it's a key.

Change-Id: I6affbfa1a79a9e8c0b5b304078a7a8e4e792eecd