wrong handling of metaclass/newstyle in rebuilder about astroid HOT 1 CLOSED

Original comment by Claudiu Popa (BitBucket: PCManticore, GitHub: @PCManticore):

Handle metaclass defined at the module level

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

from astroid.