bpo-33023: Fix NotImplemented to NotImplementedError. (GH-10934)

(cherry picked from commit 42b1d6127bd8595522a78a75166ebb9fba74a6a2)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
diff --git a/Lib/idlelib/debugger_r.py b/Lib/idlelib/debugger_r.py
index 01a3bd2..0e6dcfb 100644
--- a/Lib/idlelib/debugger_r.py
+++ b/Lib/idlelib/debugger_r.py
@@ -157,7 +157,7 @@
     #----------called by a DictProxy----------
 
     def dict_keys(self, did):
-        raise NotImplemented("dict_keys not public or pickleable")
+        raise NotImplementedError("dict_keys not public or pickleable")
 ##         dict = dicttable[did]
 ##         return dict.keys()