Apply review suggestions: shorten NEWS, use class attribute in test

Author: tonghuaroot

Lib/test/test_copy.py

@@ -941,15 +941,14 @@ def m(self):
 
     def test_deepcopy_memo_none_result(self):
         # Objects whose deepcopy result is None must still be memoized.
-        call_count = 0
         class C:
+            call_count = 0
             def __deepcopy__(self, memo):
-                nonlocal call_count
-                call_count += 1
+                C.call_count += 1
                 return None
         obj = C()
         copy.deepcopy([obj, obj, obj])
-        self.assertEqual(call_count, 1)
+        self.assertEqual(C.call_count, 1)
 
 
 class TestReplace(unittest.TestCase):

Misc/NEWS.d/next/Library/2026-07-24-00-02-00.gh-issue-154594.Xk7mQ2.rst

@@ -1,4 +1,2 @@
 Fix :func:`copy.deepcopy` so that an object whose deep copy is ``None`` is
-still memoized. The memo miss was detected with ``None``, which is a valid
-result, so such objects were copied again on every reference. Patch by
-tonghuaroot.
+still memoized. Patch by tonghuaroot.