there are two problems currently:
- SDK's `availability_zones()` returns a generator that raises errors
only when actually accessing its items
- the error raised is the sdk exception, not nova one, and thus is not
being handled correctly
As a result, currently nova AZs can not be listed by non-admins.
Story: 2010989
Task: 49220
Change-Id: Ia299faea85857d3fc3a9b539800f3483f84ccbc0
f3207bdf3f