Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/softwareproperties/gtk/SoftwarePropertiesGtk.py", line 647, in on_isv_source_toggled
    self.backend.ToggleSourceUse(str(source_entry))
  File "/usr/lib/python2.7/dist-packages/dbus/proxies.py", line 143, in __call__
    **keywords)
  File "/usr/lib/python2.7/dist-packages/dbus/connection.py", line 630, in call_blocking
    message, timeout)
DBusException: com.hostname.SoftwareProperties.PermissionDeniedByPolicy: com.hostname.softwareproperties.applychanges