<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def validate_href(image_href):
 """Validate HTTP image reference. :param image_href: Image reference. :raises: exception.ImageRefValidationFailed if HEAD request failed or returned response code not equal to 200. :returns: Response to HEAD request. """

        try:
            response = requests.head(image_href)
            if response.status_code != http_client.OK:
                raise exception.ImageRefValidationFailed(
                    image_href=image_href,
                    reason=("Got HTTP code %s instead of 200 in response to "
                            "HEAD request." % response.status_code))
        except requests.RequestException as e:
            raise exception.ImageRefValidationFailed(image_href=image_href,
                                                     reason=e)
        return response