AttributeError: 'module' object has no attribute 'Config'

[ming]

Traceback (most recent call last):
  File "/usr/bin/ubuntu-tweak", line 110, in <module>
    launcher = TweakLauncher(session_bus, MainWindow())
  File "/usr/lib/python2.6/dist-packages/ubuntutweak/mainwindow.py", line 234, in __init__
    proxy.enable_stable_source()
  File "/usr/lib/pymodules/python2.6/dbus/proxies.py", line 143, in __call__
    **keywords)
  File "/usr/lib/pymodules/python2.6/dbus/connection.py", line 630, in call_blocking
    message, timeout)
DBusException: org.freedesktop.DBus.Python.AttributeError: Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.6/dbus/service.py", line 702, in _message_cb
    retval = candidate_method(self, *args, **keywords)
  File "/usr/lib/python2.6/dist-packages/ubuntutweak/backends/daemon.py", line 216, in enable_stable_source
    'ubuntu-tweak-stable')
  File "/usr/lib/python2.6/dist-packages/ubuntutweak/backends/daemon.py", line 134, in set_separated_entry
    partsdir = apt_pkg.Config.FindDir("Dir::Etc::sourceparts")
AttributeError: 'module' object has no attribute 'Config'

[Ding Zhou (tualatrix)]

Please give me the version of your Ubuntu. Thanks.