Comment 2 for bug 1596511

cinderclient volume_type.unset_keys() only delete the first key even if multiple keys are applied.

The response of manager._delete() is tuple object, it is not "None" even if the deleting success, so the batch operation would be broken when the first key is deleted successfully, I think it's a cinderclient bug, not osc bug.

https://github.com/openstack/python-cinderclient/blob/master/cinderclient/v3/volume_types.py#L73-L74