Unauthorized results in backtrace

Bad credentials causes a nasty-looking backtrace. e.g.,
$ ./bin/swift -K junk stat
No handlers could be found for logger "keystoneclient.client"
Traceback (most recent call last):
  File "./bin/swift", line 1190, in <module>
    error_queue)
  File "./bin/swift", line 567, in st_stat
    headers = conn.head_account()

<30 lines snipped>

  File "/home/donagh/openstack/python-keystoneclient/keystoneclient/client.py", line 141, in request
    raise exceptions.from_response(resp, body)
keystoneclient.exceptions.Unauthorized: UNAUTHORIZED (HTTP 401)

The final line gives the clue, but the backtrace looks scary and will confuse novice users