':returns: URL for direct access, None if no object'

def get_object_url(self, obj, **kwargs):

    if self.exists(obj, **kwargs):
        path = self._construct_path(obj, **kwargs)
        try:
            return self.pithos.publish_object(path)
        except ClientError as ce:
            log.exception('Trouble    generating    URL    for    dataset    "{}"'.format(path))
            log.exception('Kamaki:    {0}'.format(ce))
    return None
