bpo-40275: Use new test.support helper submodules in tests (GH-21317)

diff --git a/Lib/test/test_idle.py b/Lib/test/test_idle.py
index 8bc01de..b205d35 100644
--- a/Lib/test/test_idle.py
+++ b/Lib/test/test_idle.py
@@ -1,5 +1,5 @@
 import unittest
-from test.support import import_module
+from test.support.import_helper import import_module
 
 # Skip test_idle if _tkinter wasn't built, if tkinter is missing,
 # if tcl/tk is not the 8.5+ needed for ttk widgets,