4705: Add CollectionReader.api_response() to PySDK.

The FUSE driver wants this information.
4705: Refactor mount creation in FUSE tests.
4705: Fix FUSE exception logging.

logger.exception() doesn't take the exception as an argument, it takes
a message like all the other logger methods.  It gets the exception
information from sys.exc_info().
4705: FUSE driver can read Collections that only exist in Keep.
Merge branch '4705-fuse-collections-from-keep-wip'

Closes #4705, #4708.