bpo-37483: add _PyObject_CallOneArg() function (#14558)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index f8bf45e..d012ab9 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -2258,8 +2258,7 @@
         }
 
         for (i = 0; i < saved_ob_size ; i++) {
-            keys[i] = PyObject_CallFunctionObjArgs(keyfunc, saved_ob_item[i],
-                                                   NULL);
+            keys[i] = _PyObject_CallOneArg(keyfunc, saved_ob_item[i]);
             if (keys[i] == NULL) {
                 for (i=i-1 ; i>=0 ; i--)
                     Py_DECREF(keys[i]);