Comment 1 for bug 1821187

I think the issue actually lies in the etcd interface layer. The Vault code already has the failing code behind a check for the etcd.tls.available flag, which shouldn't be set if any of those values are None.

It looks like there need to be some else conditions added to the following to remove the flag if any of the fields are cleared before the relation is broken: https://github.com/juju-solutions/interface-etcd/blob/master/requires.py#L30-L36