'Updates a snapshot.
For a full list of available parameters, please refer to the official
API reference:
http://developer.openstack.org/api-ref/block-storage/v1/#update-snapshot-v1'

def update_snapshot(self, snapshot_id, **kwargs):

    put_body = json.dumps({'snapshot': kwargs})
    (resp, body) = self.put(('snapshots/%s' % snapshot_id), put_body)
    body = json.loads(body)
    self.expected_success(200, resp.status)
    return rest_client.ResponseBody(resp, body)
