def _process_response(self, request, response):
        """Log user operation."""
        log_format = self._get_log_format(request)
        if not log_format:
            return response

        params = self._get_parameters_from_request(request)
        # log a message displayed to user
        messages = django_messages.get_messages(request)
        result_message = None
        if messages:
            result_message = ', '.join('%s: %s' % (message.tags, message)
                                       for message in messages)
        elif 'action' in request.POST:
            result_message = request.POST['action']
        params['message'] = result_message
        params['http_status'] = response.status_code

        self.OPERATION_LOG.info(log_format, params)

        return response
Log user operation.