Traceback (most recent call last):
  File "/usr/bin/software-properties-gtk", line 100, in <module>
    app = SoftwarePropertiesGtk(data_dir, options, file)
  File "/usr/lib/python2.5/site-packages/softwareproperties/gtk/SoftwarePropertiesGtk.py", line 84, in __init__
    self.window_main.set_transient_for(parent)
TypeError: parent should be a GtkWindow or None