ceph mgr RuntimeError: no certificate configured

2017-11-10 12:46:08.605552 7fcc51f1d700  0 mgr[restful] Traceback (most recent call last):
  File "/usr/lib64/ceph/mgr/restful/module.py", line 248, in serve
    self._serve()
  File "/usr/lib64/ceph/mgr/restful/module.py", line 299, in _serve
    raise RuntimeError('no certificate configured')
RuntimeError: no certificate configured

workaround:

ceph mgr module disable restful
OR
Create certificate:

ceph restful create-self-signed-cert

http://docs.ceph.com/docs/master/mgr/restful/