bpo-33987: IDLE - use ttk Frame for ttk widgets (GH-11395)

(cherry picked from commit aff0adabf3ace62073076f4ce875ff568f2d3180)

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>
diff --git a/Lib/idlelib/debugger.py b/Lib/idlelib/debugger.py
index 09f912c..ccd03e4 100644
--- a/Lib/idlelib/debugger.py
+++ b/Lib/idlelib/debugger.py
@@ -2,7 +2,7 @@
 import os
 
 from tkinter import *
-from tkinter.ttk import Scrollbar
+from tkinter.ttk import Frame, Scrollbar
 
 from idlelib import macosx
 from idlelib.scrolledlist import ScrolledList