docs: def _urllib_send(opener, req, **kwargs):
      """Send a request with an :mod:`urllib` opener"""
      if req.content and not any(h.lower() == 'content-type'
                                 for h in req.headers):
          req = req.with_headers({'Content-Type': 'application/octet-stream'})
      url = req.url + '?' + urlencode(req.params)
      raw_req = urllib_request.Request(url, req.content, headers=req.headers)
      set_urllib_method(raw_req, req.method)
      try:
          res = opener.open(raw_req, **kwargs)
      except urllib_http_error_cls as http_err:
          res = http_err
      return Response(res.getcode(), content=res.read(), headers=res.headers)