Try to fix test_spwd on OpenIndiana

Issue #18787: try to get the "root" entry which should exist on all UNIX
instead of "bin" which doesn't exist on OpenIndiana.

Lib/test/test_spwd.py

@@ -62,7 +62,7 @@ class TestSpwdNonRoot(unittest.TestCase):
 
     def test_getspnam_exception(self):
         with self.assertRaises(PermissionError) as cm:
-            spwd.getspnam('bin')
+            spwd.getspnam('root')
         self.assertEqual(str(cm.exception), '[Errno 13] Permission denied')