Keystone API version discovery

def _discover_ks_version(self, url):
        '''
        Keystone API version discovery
        '''
        result = salt.utils.http.query(url, backend='requests', status=True, decode=True, decode_type='json')
        versions = json.loads(result['body'])
        try:
            links = [ver['links'] for ver in versions['versions']['values'] if ver['status'] == 'stable'][0] \
                    if result['status'] == 300 else versions['version']['links']
            resurl = [link['href'] for link in links if link['rel'] == 'self'][0]
            return self._get_version_from_url(resurl)
        except KeyError as exc:
            raise SaltCloudSystemExit('KeyError: key {0} not found in API response: {1}'.format(exc, versions))