Code review comment for lp:~vishvananda/nova/has_role_cache

49 + def _build_mc_key(self, user, role, project=None):
50 + return str("rolecache-%s-%s-%s" % (User.safe_id(user), role,
51 + (Project.safe_id(project) if project else 'None')))

Nitpicky, but it's more accurate to use rolecache-user-role for global roles, as opposed to rolecache-user-role-None.