Added timeout parameter to DummySocket.flush

see https://github.com/ipython/ipykernel/blob/6fc9a7e9fde006a5e1f7ae40010ba8a3306af47e/ipykernel/kernelbase.py#L286

Author: Chilipp

ipykernel/inprocess/socket.py

@@ -61,7 +61,8 @@ def send_multipart(self, msg_parts, flags=0, copy=True, track=False):
         self.queue.put_nowait(msg_parts)
         self.message_sent += 1
 
-    def flush(self):
+    def flush(self, timeout=1.0):
         """no-op to comply with stream API"""
+        pass
 
 SocketABC.register(DummySocket)