Add one more testcase
PAIR/COLLECTION instead of PAIR_COLLECTION

...for statuses.

Also, various CLI usability improvements.
Saner variable names
Move status name generation in own func
Convert some logging calls to exception raises
Move "obscure" exceptions into their own modules
Catch all exceptions.

The idea is that a storage's __init__ may raise *anything* if the values
are incorrect. We already do very explicit checks whether the user
specified the wrong parameters, and show the exception if that's not the
case.