Authentication

Authentication/authorization backends belong in haas/auth_mechanisms .  It's
possible that the API of that plugin will have to be expanded to cover what
the CLI needs to do.


WIP
Changing all of the code is a lot of lowish-priority work and nobody will likely ever have the time to do it, unless we decide to catch the exception at the moc-rest layer perhaps.

If there's a more efficient/secure way of doing things, I think it's perfectly reasonable to not contribute more code that does it the old way.