tests/readlink.py

rust: upgrade `rand*` crates

`test-check-cargo-lock.t` is failing for me and I was hoping this
would help. It doesn't, but we might as well take the upgrade now that
I've done the (small amount of) work for it.

Differential Revision: https://phab.mercurial-scm.org/D12000

#!/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)