address review feedback

Author: picnixz

Lib/test/test_types.py

@@ -2170,15 +2170,17 @@ class Spam(types.SimpleNamespace):
     def test_replace_invalid_subtype(self):
         # See https://github.com/python/cpython/issues/143636.
         class NS(types.SimpleNamespace):
-            called = False
             def __new__(cls, *args, **kwargs):
-                if cls.called:
+                if created:
                     return object()
-                cls.called = True
                 return super().__new__(cls)
 
-        err = re.escape("expecting a types.SimpleNamespace object, got object")
-        self.assertRaisesRegex(TypeError, err, NS().__replace__)
+        created = False
+        ns = NS()
+        created = True
+        err = re.escape("NS.__new__() must return an instance "
+                        "of a subclass of types.SimpleNamespace")
+        self.assertRaisesRegex(TypeError, err, copy.replace, ns)
 
     def test_fake_namespace_compare(self):
         # Issue #24257: Incorrect use of PyObject_IsInstance() caused

Objects/namespaceobject.c

@@ -237,8 +237,8 @@ namespace_replace(PyObject *self, PyObject *args, PyObject *kwargs)
     }
     if (!_PyNamespace_Check(result)) {
         PyErr_Format(PyExc_TypeError,
-                     "expecting a %s object, got %T",
-                     _PyNamespace_Type.tp_name, result);
+                     "%T.__new__() must return an instance of a subclass of %s",
+                     self, _PyNamespace_Type.tp_name);
         Py_DECREF(result);
         return NULL;
     }