[root@supercomputer nova]# tail -f nova-conductor.log

  File "/usr/lib/python2.7/site-packages/nova/scheduler/manager.py", line 104, in select_destinations
    dests = self.driver.select_destinations(ctxt, spec_obj)

  File "/usr/lib/python2.7/site-packages/nova/scheduler/filter_scheduler.py", line 74, in select_destinations
    raise exception.NoValidHost(reason=reason)

NoValidHost: No valid host was found. There are not enough hosts available.

2017-02-27 21:05:11.753 22 WARNING nova.scheduler.utils [req-50968813-54be-46d8-a82c-a629a04e24f0 62d2ea98dead48a29a9c7c60ee54829b 1cb44e090edf4a4dbe19dd4545a923a7 - - -] [instance: 07788daf-227a-4d86-bedf-d5cfe8897fdd] Setting instance to ERROR state.