Traceback (most recent call last):
  File "/usr/lib/update-notifier/backend_helper.py", line 164, in <module>
    res = f(**f_kwargs)
  File "/usr/lib/update-notifier/backend_helper.py", line 122, in add_cdrom
    _add_cdrom_sp(mount_path)
  File "/usr/lib/update-notifier/backend_helper.py", line 107, in _add_cdrom_sp
    "SourcesListModified", Gtk.main_quit)
  File "/usr/lib/python2.7/dist-packages/dbus/proxies.py", line 544, in connect_to_signal
    dbus_interface, **keywords)
  File "/usr/lib/python2.7/dist-packages/dbus/proxies.py", line 369, in connect_to_signal
    **keywords)
  File "/usr/lib/python2.7/dist-packages/dbus/bus.py", line 148, in add_signal_receiver
    path, **keywords)
  File "/usr/lib/python2.7/dist-packages/dbus/connection.py", line 400, in add_signal_receiver
    self._require_main_loop()
RuntimeError: To make asynchronous calls, receive signals or export objects, D-Bus connections must be attached to a main loop by passing mainloop=... to the constructor or calling dbus.set_default_main_loop(...)