Fix websocket client already closed raise error does not match

As doc says "If the stream is closed, raises WebSocketClosedError"

diff --git a/tornado/websocket.py b/tornado/websocket.py
index c88cc2074d8d2a50427c9490c8f802c1a03802f0..f2711c94fb911b2b94ce75497e6c94b88b18495c 100644 (file)
--- a/tornado/websocket.py
+++ b/tornado/websocket.py
@@ -1501,6 +1501,8 @@ class WebSocketClientConnection(simple_httpclient._HTTPConnection):
            Exception raised on a closed stream changed from `.StreamClosedError`
            to `WebSocketClosedError`.
         """
+        if self.protocol is None:
+            raise WebSocketClosedError("Client connection has been closed")
         return self.protocol.write_message(message, binary=binary)
 
     def read_message(