ThreadedClient: schedule IOLoop.stop in IOLoop thread

calling stop doesn’t wake the IOLoop with asyncio (tornado 5)

Author: minrk

jupyter_client/threaded.py

@@ -182,7 +182,7 @@ def stop(self):
         :meth:`~threading.Thread.start` is called again.
         """
         if self.ioloop is not None:
-            self.ioloop.stop()
+            self.ioloop.add_callback(self.ioloop.stop)
         self.join()
         self.close()