There were two basic problems:
- We'd try to import on every attempt at getting auth, even when we
already know keystoneclient isn't available.
- Sometimes devs would hit some crazy import race involving (some
combination of?) greenthreads and OS threads.
So let's just try the imports *once*, at import time, and have None
sentinels if it fails. Try both versions separately to decouple
failures; this should let us support a wider range of keystoneclient
versions.
Change-Id: I2367310aac74f1b7c5ea0cb1a822a491e4ba8e68
d1e1f8d8d6