Calling Queue with no arguments throws error

[jbloom]

For slurm, calling q = Queue() or q = Queue(user=None) raises an exception, even though None is the default value of user:

>>> q = cluster.Queue(user=None)
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
   File "cluster/queue.py", line 141, in __init__
     self._update()
   File "cluster/queue.py", line 311, in _update
     self.user):
   File "cluster/queue.py", line 641, in slurm_queue_parser
     outqueue.append((sid, sname, suser, spartition, sstate, snodelist,
UnboundLocalError: local variable 'snodelist' referenced before assignment

[MikeDacre]

This should be fixed now.