bpo-40275: Use new test.support helper submodules in tests (GH-20849)

diff --git a/Lib/test/test_tix.py b/Lib/test/test_tix.py
index e6ea3d0..e6d759e 100644
--- a/Lib/test/test_tix.py
+++ b/Lib/test/test_tix.py
@@ -1,9 +1,10 @@
 import unittest
 from test import support
+from test.support import import_helper
 import sys
 
 # Skip this test if the _tkinter module wasn't built.
-_tkinter = support.import_module('_tkinter')
+_tkinter = import_helper.import_module('_tkinter')
 
 # Skip test if tk cannot be initialized.
 support.requires('gui')