use a invalid name for the __class__ closure for super() (closes #12370)

This prevents the assignment of __class__ in the class body from breaking
super. (Although a determined person could do locals()["@__class__"] = 4)
diff --git a/Misc/NEWS b/Misc/NEWS
index 89eab0e..a793d08 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@
 Core and Builtins
 -----------------
 
+- Issue #12370: Fix super with not arguments when __class__ is overriden in the
+  class body.
+
 - Issue #12084: os.stat on Windows now works properly with relative symbolic
   links when called from any directory.