tests/readlink.py

pyproject: add config file

This will tell pip et al to call our setup.py for the majority of
packaging concerns, but also gives us a place to put standard config
stuff like black.

This was previously D9833, but was rolled back due to test
breakage. nbjoerg thinks that breakage is now resolved, so we're
trying again.

Differential Revision: https://phab.mercurial-scm.org/D10184

#!/usr/bin/env python3

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)