Traceback (most recent call last):
  File "/usr/bin/jockey-gtk", line 416, in <module>
    sys.exit(u.run())
  File "/usr/lib/python2.7/dist-packages/jockey/ui.py", line 461, in run
    self.ui_show_main()
  File "/usr/bin/jockey-gtk", line 96, in ui_show_main
    self.update_tree_model()
  File "/usr/bin/jockey-gtk", line 272, in update_tree_model
    for h_id in self.get_displayed_handlers():
  File "/usr/lib/python2.7/dist-packages/jockey/ui.py", line 812, in get_displayed_handlers
    return self.backend().available(self.argv_options.mode)
  File "/usr/lib/python2.7/dist-packages/jockey/ui.py", line 123, in backend
    self._check_repositories()
  File "/usr/lib/python2.7/dist-packages/jockey/ui.py", line 845, in _check_repositories
    self._repository_progress_handler})
  File "/usr/lib/python2.7/dist-packages/jockey/backend.py", line 107, in convert_dbus_exceptions
    raise SystemError(str(e))
SystemError: org.freedesktop.DBus.Python.SystemError: Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/dbus/service.py", line 702, in _message_cb
    retval = candidate_method(self, *args, **keywords)
  File "/usr/lib/python2.7/dist-packages/jockey/backend.py", line 602, in update_repository_indexes
    hasattr(self, '_locations') and self.repository_update_progress or None)
  File "/usr/lib/python2.7/dist-packages/jockey/oslib.py", line 434, in update_repository_indexes
    raise SystemError(str(e))
SystemError: Failed to lock /var/lib/apt/lists/lock