tests/readlink.py

tests: better testing of loaded certificates

Tests were failing on systems like RHEL 7 where loading the system
certificates results in CA certs being reported to Python. We add
a feature that detects when we're able to load *and detect* the
loading of system certificates. We update the tests to cover the
3 scenarios:

1) system CAs are loadable and detected
2) system CAs are loadable but not detected
3) system CAs aren't loadable

#!/usr/bin/env python

from __future__ import print_function

import errno, os, 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)