And avoid stack traces like::

  Traceback (most recent call last):
    File "/usr/lib/python2.7/threading.py", line 783, in __bootstrap
      self.__bootstrap_inner()
    File "/usr/lib/python2.7/threading.py", line 810, in __bootstrap_inner
      self.run()
    File "/usr/lib/python2.7/threading.py", line 763, in run
      self.__target(*self.__args, **self.__kwargs)
  --- <exception caught here> ---
    [...]
    File "/usr/lib/python2.7/dist-packages/twisted/python/threadpool.py", line 196, in _worker
      result = context.call(ctx, function, *args, **kwargs)
    File "/usr/lib/python2.7/dist-packages/twisted/python/context.py", line 118, in callWithContext
      return self.currentContext().callWithContext(ctx, func, *args, **kw)
    File "/usr/lib/python2.7/dist-packages/twisted/python/context.py", line 81, in callWithContext
      return func(*args,**kw)
    File "/home/me/envs/grshell-cw/cubicweb/statsd_logger.py", line 121, in __call__
      return self.callable(*args, **kw)
    File "/home/me/envs/grshell-cw/cubicweb/etwist/server.py", line 131, in render_request
      code=500, twisted_request=request)
    File "/home/me/envs/grshell-cw/cubicweb/etwist/http.py", line 22, in __init__
      self._finalize()
    File "/home/me/envs/grshell-cw/cubicweb/etwist/http.py", line 46, in _finalize
      self._twreq.finish()
    File "/usr/lib/python2.7/dist-packages/twisted/web/server.py", line 228, in finish
      return http.Request.finish(self)
    File "/usr/lib/python2.7/dist-packages/twisted/web/http.py", line 931, in finish
      "Request.finish called on a request after its connection was lost; "
  exceptions.RuntimeError: Request.finish called on a request after its connection was lost; use Request.notifyFinish to keep track of this.