(I'll also note that my final comment there is rather different from my first draft, as I almost forgot myself that the namespace preparation logic lives in __build_class__ rather than type_new. Class definitions can actually bypass type entirely, even in Python 3:

>>> def the_one_class(*args):
...     return 1
... 
>>> class TheOne(metaclass=the_one_class): pass
... 
>>> TheOne
1