Python Swift client ConnectionError: [Errno 9] File descriptor was closed in another greenlet

I'm seeing the following exception about 10% of the time when load testing a private Docker registry instance which is relying on the Python-swiftclient v2.2.0 on Ubuntu 14.04 to upload chunked image layers to Swift storage. Any help in resolving this error would be much appreciated.

ClientException: put_object('community-registry', 'registry/images/3f4e063c79399251dafe66c85da9a17eb735fb3f6281a9278033ad6cb5822c70/layer', ...) failure and no ability to reset contents for reupload.
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/swiftclient/client.py", line 1211, in _retry
    rv = func(self.url, self.token, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/swiftclient/client.py", line 959, in put_object
    conn.putrequest(path, headers=headers, data=chunk_reader())
  File "/usr/local/lib/python2.7/dist-packages/swiftclient/client.py", line 224, in putrequest
    return self.request('PUT', full_path, data, headers, files)
  File "/usr/local/lib/python2.7/dist-packages/swiftclient/client.py", line 214, in request
    files=files, **self.requests_args)
  File "/usr/local/lib/python2.7/dist-packages/swiftclient/client.py", line 182, in _request
    return self.request_session.request(*arg, **kwarg)
  File "/usr/local/lib/python2.7/dist-packages/requests/sessions.py", line 456, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/local/lib/python2.7/dist-packages/requests/sessions.py", line 559, in send
    r = adapter.send(request, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/requests/adapters.py", line 372, in send
    raise ConnectionError(sockerr, request=request)
ConnectionError: [Errno 9] File descriptor was closed in another greenlet

Thanks!