'Generates a Swift backup object name prefix.'

def _generate_object_name_prefix(self, backup):

    az = ('az_%s' % self.az)
    backup_name = ('%s_backup_%s' % (az, backup['id']))
    volume = ('volume_%s' % backup['volume_id'])
    timestamp = timeutils.utcnow().strftime('%Y%m%d%H%M%S')
    prefix = ((((volume + '/') + timestamp) + '/') + backup_name)
    LOG.debug('generate_object_name_prefix:    %s', prefix)
    return prefix
