It doesn't help:

ERROR: test_default_property (test._gc.AbstractGCProtectorTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/paul/notify/test/_gc.py", line 59, in test_default_property
    AbstractGCProtector.set_default (original_protector)
TypeError: can't set attributes of built-in/extension type
'notify.gc.AbstractGCProtector'

With this code:

  if (PyObject_SetAttrString ((PyObject *) &AbstractGCProtector_Type,
"default", new_protector)
      == -1)
    return NULL;