sphinx_automodapi/automodsumm.py: address #132

The members of ABC-derived classes were not being listed when they used
a custom metaclass deriving from ABCMeta. The fix is not just test for
exact equality of the ABCMeta metaclass, but subclassness.

sphinx_automodapi/automodsumm.py

@@ -539,7 +539,7 @@ def get_members_class(obj, typ, include_public=[],
                     # class `__dict__` instead.
                     declares_slots = (
                         hasattr(obj, '__slots__') and
-                        not (type(obj) is abc.ABCMeta and
+                        not (issubclass(type(obj), abc.ABCMeta) and
                              len(obj.__slots__) == 0)
                     )