Traceback (most recent call last):
  File "/usr/lib/python2.6/dist-packages/aptdaemon/defer.py", line 427, in defer
    result = func(*args, **kwargs)
  File "/usr/lib/python2.6/dist-packages/aptdaemon/errors.py", line 139, in _convert_dbus_exception
    raise get_native_exception(error)
TransactionFailed: org.debian.apt.TransactionFailed: error-cache-broken:  gnome-session