Metaclass with Any type should be allowed #2911

This should work:

from typing import Any
M = None # type: Any
class C(metaclass=M): pass

Currently M is considered an invalid metaclass.

Also, it should be possible to use a class that is imported from a missing module as a metaclass when using --ignore-missing-imports.

The simplest fix is to just ignore such metaclasses, though a better approach may be to treat them in a similar way as an Any base class (but only for class attributes).