code: def keyring(cluster, hostname):
      
      keyring_file = '%s-%s.mon.keyring' % (cluster, hostname)
      return join(constants.tmp_path, keyring_file)
docs: Example usage::
  
          >>> from ceph_deploy.util.paths import mon
          >>> mon.keyring('mycluster', 'myhostname')
          /var/lib/ceph/tmp/mycluster-myhostname.mon.keyring