upate code

Author: chengcong1

jupyter_server/gateway/connections.py

@@ -146,7 +146,7 @@ def handle_outgoing_message(self, incoming_msg: str, *args: Any) -> None:
     def handle_incoming_message(self, message: str) -> None:
         """Send message to gateway server."""
         if self.ws is None and self.ws_future is not None:
-            if self.ws_future.done() and isinstance(self.ws_future.exception, Exception):
+            if self.ws_future.done() and isinstance(self.ws_future.exception(), Exception):
                 self.log.warning(f"Exception connect to websocket {self.ws_future.exception()}")
                 return
             loop = IOLoop.current()