tests/readlink.py

tests: allow [Errno] in output

I'm not sure why, but my system is printing "[Errno -5]" before
the "No address associated with hostname" message. I suspect a
modern version of Python improved errno tracking or something.

Add an "[Errno ...]" pattern as optional output to make the test
pass.

Differential Revision: https://phab.mercurial-scm.org/D1958

#!/usr/bin/env python

from __future__ import absolute_import, print_function

import errno
import os
import sys

for f in sys.argv[1:]:
    try:
        print(f, '->', os.readlink(f))
    except OSError as err:
        if err.errno != errno.EINVAL:
            raise
        print(f, '->', f, 'not a symlink')

sys.exit(0)