I have a twisted server. And I have been seeing this annoying issue.

Normally. when i develop and test it out. everything is fine..
But then I try to loadtest is via https://locust.io/

Again, everything is fine.. until I "stop" the test.

Then, I see this
'Traceback (most recent call last):\n  File "/usr/local/Cellar/python/3.7.1/Frameworks/Python.framework/Versions/3.7/lib/python3.7/asyncio/events.py", line 88, in _run\n    self._context.run(self._callback, *self._args)\n  File "/usr/local/lib/python3.7/site-packages/twisted/internet/defer.py", line 827, in adapt\n    adapt.actual.callback(extracted)\n  File "/usr/local/lib/python3.7/site-packages/twisted/internet/defer.py", line 460, in callback\n    self._startRunCallbacks(result)\n  File "/usr/local/lib/python3.7/site-packages/twisted/internet/defer.py", line 568, in _startRunCallbacks\n    self._runCallbacks()\n--- <exception caught here> ---\n  File "/usr/local/lib/python3.7/site-packages/twisted/internet/defer.py", line 654, in _runCallbacks\n    current.result = callback(current.result, *args, **kw)\n  File 

....

 File "/usr/local/lib/python3.7/site-packages/twisted/web/server.py", line 238, in write\n    http.Request.write(self, data)\n  File "/usr/local/lib/python3.7/site-packages/twisted/web/http.py", line 1118, in write\n    self.channel.writeHeaders(version, code, reason, headers)\nbuiltins.AttributeError: \'NoneType\' object has no attribute \'writeHeaders\'\n'

I found this similar bug report: https://github.com/buildbot/buildbot/issues/4045

But I am using 19.2.1 twisted version..

Again, this is only triggered when I "stop" the locust io test.

Any suggestions?