def _open_terminal():
    """Open pty master and return (master_fd, tty_name)."""
    for x in 'pqrstuvwxyzPQRST':
        for y in '0123456789abcdef':
            pty_name = '/dev/pty' + x + y
            try:
                fd = os.open(pty_name, os.O_RDWR)
            except OSError:
                continue
            return (fd, '/dev/tty' + x + y)
    raise OSError('out of pty devices')
Open pty master and return (master_fd, tty_name).