Traceback (most recent call last):
  File "/usr/share/software-center/softwarecenter/app.py", line 358, in on_menuitem_software_sources_activate
    self.run_update_cache()
  File "/usr/share/software-center/softwarecenter/app.py", line 401, in run_update_cache
    trans = aptd_client.update_cache(exit_handler=self._on_trans_finished)
TypeError: update_cache() got an unexpected keyword argument 'exit_handler'