tests/readlink.py

run-tests.py: avoid using popen2.Popen4 - use subprocess instead

Use subprocess to emulate Popen4 if available - similar to how it is done in
util.py.

Using popen2 under python 2.6 gives
DeprecationWarning: The popen2 module is deprecated.  Use the subprocess module.

#!/usr/bin/env python

import errno, os, sys

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

sys.exit(0)