Comment 1 for bug 1606551

The issue is in prod, because in nova logs you can find trace from nova:
Traceback (most recent call last):

  File "/usr/lib/python2.7/dist-packages/oslo_messaging/rpc/server.py", line 150, in inner
    return func(*args, **kwargs)

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

  File "/usr/lib/python2.7/dist-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.