ceph-osd reports hook failed, but it worked

[Zoltan Arnold Nagy]

after a fresh deploy with separate monitors with the ceph charm and separate osds with the ceph-osd charm, if I run "juju add-relation ceph ceph-osd" this happens:

      ceph-osd/1:
        workload-status:
          current: error
          message: 'hook failed: "mon-relation-changed" for ceph:osd'
          since: 06 Feb 2016 23:59:20+01:00
        agent-status:
          current: idle
          since: 06 Feb 2016 23:59:20+01:00
          version: 1.25.3.1
        agent-state: error
        agent-state-info: 'hook failed: "mon-relation-changed" for ceph:osd'
        agent-version: 1.25.3.1
        machine: "5"
        public-address: xxxxx
      ceph-osd/2:
        workload-status:
          current: error
          message: 'hook failed: "mon-relation-changed" for ceph:osd'
          since: 06 Feb 2016 23:59:17+01:00
        agent-status:
          current: idle
          since: 06 Feb 2016 23:59:17+01:00
          version: 1.25.3.1
        agent-state: error
        agent-state-info: 'hook failed: "mon-relation-changed" for ceph:osd'
        agent-version: 1.25.3.1
        machine: "6"
        public-address: xxxxx

HOWEVER, the OSDs are created fine and added to the ceph cluster:

ubuntu@c01n4:~$ sudo ceph -s
[...]
     osdmap e31: 12 osds: 12 up, 12 in
[...]