Comment 2 for bug 1984118

I hit similar issue, vault was related to ceph-radosgw via cross-model-relation, CA was missing with one of the vault units (vault/1). When ran certificates-relation-changed hook, it tried to get CA from vault/1, got 'NoneType' exception

$ juju show-unit ceph-radosgw/5 |grep ca: -C3
      vault/0:
        in-scope: true
        data:
          ca: |-
            -----BEGIN CERTIFICATE-----

--
      vault/2:
        in-scope: true
        data:
          ca: |-
            -----BEGIN CERTIFICATE-----

>>>>>>>juju log

unit-cross-site-rgw-ceph-radosgw-3: 01:41:30 WARNING unit.cross-site-rgw-ceph-radosgw/3.certificates-relation-changed _manage_ca_certs(ca, relation_id)
unit-cross-site-rgw-ceph-radosgw-3: 01:41:30 WARNING unit.cross-site-rgw-ceph-radosgw/3.certificates-relation-changed File "/var/lib/juju/agents/unit-cross-site-rgw-ceph-radosgw-3/charm/hooks/charmhelpers/contrib/openstack/cert_utils.py", line 351, in _manage_ca_certs
unit-cross-site-rgw-ceph-radosgw-3: 01:41:30 WARNING unit.cross-site-rgw-ceph-radosgw/3.certificates-relation-changed ca.encode(),
unit-cross-site-rgw-ceph-radosgw-3: 01:41:30 WARNING unit.cross-site-rgw-ceph-radosgw/3.certificates-relation-changed AttributeError: 'NoneType' object has no attribute 'encode'