Older versions of multiprocessing closed fd 0

Problem
=======

Per, https://docs.python.org/2/library/multiprocessing.html#all-platforms

""" multiprocessing originally unconditionally called:

        os.close(sys.stdin.fileno())

    in the multiprocessing.Process._bootstrap() method
"""

Solution
========

We simulate in test case by using multiprocessing module
and closing stdin before calling pexpect.spawn.

Change use of __stdin__.fileno() with __stdout__.fileno(), for
tcgetattr(3), any of stdin/out/err is fine. Then, allow for
ValueError("I/O operation on closed file") could be raised
if stdout is closed, and make another test case where we close
it as such.