Add optimization reminder.

mayan/apps/acls/managers.py

@@ -59,6 +59,7 @@ class AccessControlListManager(models.Manager):
 
                 user_roles.append(role)
 
+        # TODO: possible .exists() optimization
         if not self.filter(content_type=ContentType.objects.get_for_model(obj), object_id=obj.pk, permissions__in=stored_permissions, role__in=user_roles):
             raise PermissionDenied(ugettext('Insufficient access.'))