bzr-notify: add_action() takes exactly 6 arguments (5 given)

After update to Precise Pangolin I am seeing the following errors in .xsession-errors and the notification has stopped working:

ERROR:dbus.connection:Exception in handler for D-Bus signal:
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/dbus/connection.py", line 230, in maybe_handle_message
    self._handler(*args, **kwargs)
  File "/usr/bin/bzr-notify", line 84, in catch_branch
    nw.add_action("inspect", "Inspect", start_viz, None)
  File "/usr/lib/python2.7/dist-packages/gi/types.py", line 43, in function
    return info.invoke(*args, **kwargs)
TypeError: add_action() takes exactly 6 arguments (5 given)