It is unsafe to copy users tasks results (since we can not guarnatee they are copyable, even using copy.copy which does a shallow copy); this causes issues like the following with sqlalchemy results:

'''2015-05-07 22:42:51.142 17040 TRACE oslo_messaging. rpc.dispatcher ObjectDereferen cedError: Can't emit change event for attribute 'Volume. provider_ location' - parent object of type <Volume> has been garbage collected.'''

'Exception during message handling: Can't emit change event for attribute 'Volume. provider_ location' - parent object of type <Volume> has been garbage collected.'''