The problem is GObject.Object.__init__ is what ends up creating the backing GObject so when this is not call, the held GObject pointer will be NULL:

from gi.repository import GObject

class Spam(GObject.Object):
    def __init__(self):
        pass  # super __init__ is not called.

spam = Spam()
spam.notify('eggs')

Warning: g_object_notify: assertion 'G_IS_OBJECT (object)' failed
  #!/usr/bin/python3


We should raise an exception if a method is called and the GObject pointer for "self" is NULL.