test_pep277: format filename with ascii() on failure

"%a" instead of "%r"
diff --git a/Lib/test/test_pep277.py b/Lib/test/test_pep277.py
index eff7ba4..f1b7a59 100644
--- a/Lib/test/test_pep277.py
+++ b/Lib/test/test_pep277.py
@@ -99,7 +99,7 @@
             filename = filename.encode(sys.getfilesystemencoding())
         if check_fn_in_exception:
             self.assertEqual(exc_filename, filename, "Function '%s(%a) failed "
-                             "with bad filename in the exception: %r" %
+                             "with bad filename in the exception: %a" %
                              (fn.__name__, filename, exc_filename))
 
     def test_failures(self):