Issue #24745: Prevent IDLE initialization crash with Tk 8.4; patch by Ned Deily.

Lib/idlelib/configHandler.py

@@ -22,6 +22,7 @@ import os
 import sys
 
 from configparser import ConfigParser
+from tkinter import TkVersion
 from tkinter.font import Font, nametofont
 
 class InvalidConfigType(Exception): pass
@@ -688,6 +689,9 @@ class IdleConf:
         bold = self.GetOption(configType, section, 'font-bold', default=0,
                               type='bool')
         if (family == 'TkFixedFont'):
+            if TkVersion < 8.5:
+                family = 'Courier'
+            else:
                 f = Font(name='TkFixedFont', exists=True, root=root)
                 actualFont = Font.actual(f)
                 family = actualFont['family']