Add an assertion instead of a comment for newargs.

Author: ZeroIntensity

Objects/genericaliasobject.c

@@ -542,7 +542,7 @@ _Py_subs_parameters(PyObject *self, PyObject *args, PyObject *parameters, PyObje
             if (jarg < 0) {
                 Py_DECREF(item);
                 Py_XDECREF(tuple_args);
-                /* newargs was stolen */
+                assert(newargs == NULL);
                 return NULL;
             }
         }