check if base_url set before passing it to HubOAuth
@@ -83,7 +83,7 @@ if allow_origin:
if os.getenv('BUILD_NAMESPACE'):
c.BinderHub.build_namespace = os.environ['BUILD_NAMESPACE']
-if c.BinderHub.auth_enabled:
+if c.BinderHub.auth_enabled and 'base_url' in c.BinderHub:
c.HubOAuth.base_url = c.BinderHub.base_url
# load extra config snippets
