'Returns an error if prerequisites aren\'t met.'

def check_for_setup_error(self):

    if ((rados is None) or (rbd is None)):
        msg = _('rados    and    rbd    python    libraries    not    found')
        raise exception.BackupDriverException(message=msg)
    for attr in ['backup_ceph_user', 'backup_ceph_pool', 'backup_ceph_conf']:
        val = getattr(CONF, attr)
        if (not val):
            raise exception.InvalidConfigurationValue(option=attr, value=val)
    with rbd_driver.RADOSClient(self, self._ceph_backup_pool):
        pass
