[3.14] pythongh-130655: gettext: Add fallback testcase (pythonGH-136857) (python#136862)

pythongh-130655: gettext: Add fallback testcase (pythonGH-136857)
(cherry picked from commit c6e6fe9)

Co-authored-by: Dominic H <dom@dominic.sk>

Author: miss-islington

Lib/test/test_gettext.py

@@ -937,6 +937,13 @@ def test_lazy_import(self):
         ensure_lazy_imports("gettext", {"re", "warnings", "locale"})
 
 
+class TranslationFallbackTestCase(unittest.TestCase):
+    def test_translation_fallback(self):
+        with os_helper.temp_cwd() as tempdir:
+            t = gettext.translation('gettext', localedir=tempdir, fallback=True)
+            self.assertIsInstance(t, gettext.NullTranslations)
+
+
 if __name__ == '__main__':
     unittest.main()