misc: don't do anything if CUT_GNM_OU_MAPPING is missing

src/authentic2_gnm/__init__.py

@@ -24,6 +24,8 @@ class AppConfig(django.apps.AppConfig):
     name = 'authentic2_gnm'
 
     def a2_hook_auth_oidc_backend_modify_user(self, user, user_info, **kwargs):
+        if not hasattr(settings, 'CUT_GNM_OU_MAPPING'):
+            return False
         ou_map = {ou.slug: ou for ou in get_ou_model().cached()}
         # move user to the correct organizational unit
         user_ou_slug = settings.CUT_GNM_OU_MAPPING.get(user_info.get('ou'))