bpo-40275: Use new test.support helper submodules in tests (GH-21743)

diff --git a/Lib/test/test_tabnanny.py b/Lib/test/test_tabnanny.py
index 95840d6..4dfbd29 100644
--- a/Lib/test/test_tabnanny.py
+++ b/Lib/test/test_tabnanny.py
@@ -12,7 +12,8 @@
 import tempfile
 import textwrap
 from test.support import (captured_stderr, captured_stdout, script_helper,
-                          findfile, unlink)
+                          findfile)
+from test.support.os_helper import unlink
 
 
 SOURCE_CODES = {