Before `RequestHandler.flush` was called, we got the final _write_buffer.

        This method will not be called in wsgi mode

def flush(self, *args, **kwgs):
        """
        Before `RequestHandler.flush` was called, we got the final _write_buffer.

        This method will not be called in wsgi mode
        """
        if settings['LOG_RESPONSE'] and not self._status_code == 500:
            log_response(self)

        super(BaseHandler, self).flush(*args, **kwgs)