bpo-45059: Add module cleanup to IDLE test_macosx (GH-28102)

Lib/idlelib/idle_test/test_macosx.py

diff --git a/Lib/idlelib/idle_test/test_macosx.py b/Lib/idlelib/idle_test/test_macosx.py
index 1932477..86da884 100644
--- a/Lib/idlelib/idle_test/test_macosx.py
+++ b/Lib/idlelib/idle_test/test_macosx.py
@@ -12,6 +12,15 @@
 alltypes = mactypes | nontypes
 
 
+def setUpModule():
+    global orig_tktype
+    orig_tktype = macosx._tk_type
+
+
+def tearDownModule():
+    macosx._tk_type = orig_tktype
+
+
 class InitTktypeTest(unittest.TestCase):
     "Test _init_tk_type."