Don't use sebTest() in tests for issue #5815.
diff --git a/Lib/test/test_locale.py b/Lib/test/test_locale.py
index f19c6c5..b554d77 100644
--- a/Lib/test/test_locale.py
+++ b/Lib/test/test_locale.py
@@ -378,8 +378,7 @@
 
     def test_locale_alias(self):
         for localename, alias in locale.locale_alias.items():
-            with self.subTest(locale=(localename, alias)):
-                self.check(localename, alias)
+            self.check(localename, alias)
 
     def test_empty(self):
         self.check('', '')