Close #14857: fix regression in references to PEP 3135 implicit __class__ closure variable. Reopens issue #12370, but also updates unittest.mock to workaround that issue

Lib/test/test_super.py

@@ -81,6 +81,7 @@ class TestSuper(unittest.TestCase):
 
         self.assertEqual(E().f(), 'AE')
 
+    @unittest.expectedFailure
     def test___class___set(self):
         # See issue #12370
         class X(A):
@@ -91,6 +92,29 @@ class TestSuper(unittest.TestCase):
         self.assertEqual(x.f(), 'A')
         self.assertEqual(x.__class__, 413)
 
+    def test___class___instancemethod(self):
+        # See issue #14857
+        class X:
+            def f(self):
+                return __class__
+        self.assertIs(X().f(), X)
+
+    def test___class___classmethod(self):
+        # See issue #14857
+        class X:
+            @classmethod
+            def f(cls):
+                return __class__
+        self.assertIs(X.f(), X)
+
+    def test___class___staticmethod(self):
+        # See issue #14857
+        class X:
+            @staticmethod
+            def f():
+                return __class__
+        self.assertIs(X.f(), X)
+
 
 def test_main():
     support.run_unittest(TestSuper)