Fix the mock homserver used in the tests

tests/utils.py

@@ -49,6 +49,7 @@ def setup_test_homeserver(name="test", datastore=None, config=None, **kargs):
         config.disable_registration = False
         config.macaroon_secret_key = "not even a little secret"
         config.server_name = "server.under.test"
+        config.trusted_third_party_id_servers = []
 
     if "clock" not in kargs:
         kargs["clock"] = MockClock()