nova-volumes does not properly raise exception when an unknown zone is passed

[Joshua Tobin]

When trying to create a new volume using "euca-create-volume", if a zone that does not exist is passed, nova does not complain about the non-existent zone, if fails silently to the user, and the volume hangs indefinitely in the creation process.

Example:

First try and create a new volume

   $ euca-create-volume -s 2 -z RegionOne

Looking at the volumes you'll see it hangs forever in creating.
   $ euca-describe-volumes
      VOLUME vol-00000002 2 RegionOne creating 2012-04-26T16:19:52.000Z

nova-scheduler.log throws an exception, but is never passed back to the user.

*************************
9 a3cdb0db4ad147e2976b5e6accdb1949] Failed to schedule_create_volume: No valid host was found. Is the appropriate service running?
2012-04-26 09:19:53 ERROR nova.rpc.amqp [req-ea12314f-2c72-4945-9147-4faf34ac423b 1376e6236a6b491da47353a5e7961349 a3cdb0db4ad147e2976b5e6accdb1949] Exception during message handling
2012-04-26 09:19:53 TRACE nova.rpc.amqp Traceback (most recent call last):
2012-04-26 09:19:53 TRACE nova.rpc.amqp File "/usr/lib/python2.7/dist-packages/nova/rpc/amqp.py", line 252, in _process_data
2012-04-26 09:19:53 TRACE nova.rpc.amqp rval = node_func(context=ctxt, **node_args)
2012-04-26 09:19:53 TRACE nova.rpc.amqp File "/usr/lib/python2.7/dist-packages/nova/scheduler/manager.py", line 97, in _schedule
2012-04-26 09:19:53 TRACE nova.rpc.amqp context, ex, *args, **kwargs)
2012-04-26 09:19:53 TRACE nova.rpc.amqp File "/usr/lib/python2.7/contextlib.py", line 24, in __exit__
2012-04-26 09:19:53 TRACE nova.rpc.amqp self.gen.next()
2012-04-26 09:19:53 TRACE nova.rpc.amqp File "/usr/lib/python2.7/dist-packages/nova/scheduler/manager.py", line 92, in _schedule
2012-04-26 09:19:53 TRACE nova.rpc.amqp return driver_method(*args, **kwargs)
2012-04-26 09:19:53 TRACE nova.rpc.amqp File "/usr/lib/python2.7/dist-packages/nova/scheduler/simple.py", line 144, in schedule_create_volume
2012-04-26 09:19:53 TRACE nova.rpc.amqp raise exception.NoValidHost(reason=msg)
2012-04-26 09:19:53 TRACE nova.rpc.amqp NoValidHost: No valid host was found. Is the appropriate service running?
2012-04-26 09:19:53 TRACE nova.rpc.amqp