This makes the pseudo-terminal the controlling tty. This should be
    more portable than the pty.fork() function. Specifically, this should
    work on Solaris.

def pty_make_controlling_tty(tty_fd):
    '''This makes the pseudo-terminal the controlling tty. This should be
    more portable than the pty.fork() function. Specifically, this should
    work on Solaris. '''

    child_name = os.ttyname(tty_fd)

    # Disconnect from controlling tty, if any.  Raises OSError of ENXIO
    # if there was no controlling tty to begin with, such as when
    # executed by a cron(1) job.
    try:
        fd = os.open("/dev/tty", os.O_RDWR | os.O_NOCTTY)
        os.close(fd)
    except OSError as err:
        if err.errno != errno.ENXIO:
            raise

    os.setsid()

    # Verify we are disconnected from controlling tty by attempting to open
    # it again.  We expect that OSError of ENXIO should always be raised.
    try:
        fd = os.open("/dev/tty", os.O_RDWR | os.O_NOCTTY)
        os.close(fd)
        raise PtyProcessError("OSError of errno.ENXIO should be raised.")
    except OSError as err:
        if err.errno != errno.ENXIO:
            raise

    # Verify we can open child pty.
    fd = os.open(child_name, os.O_RDWR)
    os.close(fd)

    # Verify we now have a controlling tty.
    fd = os.open("/dev/tty", os.O_WRONLY)
    os.close(fd)