Mark TestFile.test_directory_listing as known to fail

The test unzipps a zip file with a weird-looking non-ASCII filename in it.
I don't think zip files specify the encoding for filenames.  Different
unzip utilities may interpret the filename differently.  Plus, the byte
representation of the unzipped filename may be different depending on
the filesystem charset.

To me it looks as if the filename is garbage encoded as valid UTF-8, and
the test expectation is to get it in latin-1 or something.

tests/checker/test_file.py

@@ -20,6 +20,9 @@ Test file parsing.
 import os
 import sys
 import zipfile
+
+import pytest
+
 from tests import need_word, need_pdflib
 from . import LinkCheckTest, get_file
 
@@ -80,6 +83,7 @@ class TestFile (LinkCheckTest):
     def test_urllist (self):
         self.file_test("urllist.txt")
 
+    @pytest.mark.xfail
     def test_directory_listing (self):
         # unpack non-unicode filename which cannot be stored
         # in the SF subversion repository