Summary:
Ref T8449. If a user doesn't have access to any spaces, most applications just don't work, and they fail in confusing ways.
Just lock users out of everything explicitly up front with a clear message instead of letting them stumble into a big broken mess.
Test Plan: Locked a user out of all spaces, saw error to that effect.
Reviewers: btrahan, eadler
Reviewed By: eadler
Subscribers: eadler, epriestley
Maniphest Tasks: T8449
Differential Revision: https://secure.phabricator.com/D13545
