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
diff --git a/Python/compile.c b/Python/compile.c
index 10e9ad2..2a1b754 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -1676,7 +1676,7 @@
             return 0;
         }
         /* return the (empty) __class__ cell */
-        str = PyUnicode_InternFromString("@__class__");
+        str = PyUnicode_InternFromString("__class__");
         if (str == NULL) {
             compiler_exit_scope(c);
             return 0;