Traceback (most recent call last):
  File "/usr/bin/hp-toolbox", line 254, in <module>
    toolbox = DevMgr5(__version__, device_uri,  None)
  File "/usr/share/hplip/ui4/devmgr5.py", line 182, in __init__
    self.user_settings = UserSettings()
  File "/usr/share/hplip/ui4/ui_utils.py", line 98, in __init__
    QSettings.__init__(self, os.path.join(prop.user_dir,  'hplip.conf'),  QSettings.IniFormat)
  File "/usr/lib/python2.6/posixpath.py", line 67, in join
    elif path == '' or path.endswith('/'):
AttributeError: 'NoneType' object has no attribute 'endswith'