Raises stored :class:`HTTPError` or :class:`URLError`, if occurred.

def raise_for_status(self):
        """Raises stored :class:`HTTPError` or :class:`URLError`, if occurred.
        """
        if not self.ok:
            reason = self.reason or 'No response from %s' % self.url
            if not self.status_code:
                raise HttpConnectionError(reason, response=self)

            if 400 <= self.status_code < 500:
                http_error_msg = '%s Client Error - %s - %s %s' % (
                    self.status_code, reason, self.request.method, self.url)
            else:
                http_error_msg = '%s Server Error - %s - %s %s' % (
                    self.status_code, reason, self.request.method, self.url)

            raise HttpRequestException(http_error_msg, response=self)