stubtest: distinguish metaclass attributes from class attributes

If the runtime attribute of a class is actually from the metaclass,
consider it to be MISSING at runtime.

Author: tungol

mypy/stubtest.py

@@ -568,6 +568,13 @@ def verify_typeinfo(
             # Catch all exceptions in case the runtime raises an unexpected exception
             # from __getattr__ or similar.
             continue
+
+        # If it came from the metaclass, consider the runtime_attr to be MISSING
+        # for a more accurate message
+        if runtime_attr is not MISSING and type(runtime) != runtime:
+            if getattr(runtime_attr, "__objclass__", None) is type(runtime):
+                runtime_attr = MISSING
+
         # Do not error for an object missing from the stub
         # If the runtime object is a types.WrapperDescriptorType object
         # and has a non-special dunder name.