According to the doc
(https://docs.python.org/2/reference/datamodel.html#customizing-class-creation):
The appropriate metaclass is determined by the following precedence rules:
- If dict['__metaclass__'] exists, it is used.
- Otherwise, if there is at least one base class, its metaclass is used
(this looks for a __class__ attribute first and if not found, uses its
type).
- Otherwise, if a global variable named __metaclass__ exists, it is used.
- Otherwise, the old-style, classic metaclass (types.ClassType) is used.
The third case was not handled by node.metaclass().
Remove metaclass lookup from the rebuilder, handle it all in
Class._explicit_metaclass() instead, and use that in _newstyle_impl if
possible.
Remove test_newstyle_and_metaclass_bad, as I think the returned value in
this test is irrelevant (it's a TypeError anyway, so you can't actually
build that class), and replace it with a test using nested classes.
Closes issue#33