[pygtk] How to widget.queue_draw_region(cairo.Region) with Gtk+ 3.0

[Just Fill Bugs]

It seems that cairo.Region replaced gdk.Rectangle in Gtk 3.0. However, 
the cairo.Region was not wrapped anywhere. How do we invalidate parts of 
a widget for redraw? I got:

     self.drawing_area.queue_draw_region(rect)
   File "/usr/lib/python2.7/site-packages/gi/types.py", line 44, in function
     return info.invoke(*args)
TypeError: Couldn't find conversion for foreign struct 'cairo.Region'