* So flask.g.fas_user.groups does not contain any of the cla groups? (I know we discussed this earlier; just can't remember the outcome).

* I'd also be okay with doing this slightly hackily if needed:
  len(g for g in flask.g.fas_user.groups if not g.startswith('cla_')) <= 0

* I like testing on the len() of groups better than checking for equality to empty list.  I could see someone changing .groups from a list into a set/frozenset in the future and not seeing that they'd need to change this at the same time.  (Also inequalities protect you from unforeseen problems better than equals).