How do I properly override __setattr__ and __getattribute__ on new-style classes in Python?
It's
super(ABCImmutable, self).__setattr__(name, value)in Python 2, or
super().__setattr__(name, value)in Python 3.
Also, raising AttributeError is not how you fall back to the default behavior for __getattribute__. You fall back to the default with
return super(ABCImmutable, self).__getattribute__(name)on Python 2 or
return super().__getattribute__(name)on Python 3.
Raising AttributeError skips the default handling and goes to __getattr__, or just produces an AttributeError in the calling code if there's no __getattr__.
See the documentation on Customizing Attribute Access.