Asking user for confirmation from RedHat kickstart pre-installation script

ks-pre-dialog.py

%pre --interpreter /usr/bin/python
# -*- coding: utf-8 -*-
import os, sys
from snack import *

def set_tty(n):
    f = open('/dev/tty%d' % n, 'a')
    os.dup2(f.fileno(), sys.stdin.fileno())
    os.dup2(f.fileno(), sys.stdout.fileno())
    os.dup2(f.fileno(), sys.stderr.fileno())

set_tty(1)
screen = SnackScreen()

def CheckCancel(ret):
    if ret == 'cancel':
        screen.finish();
        os.execlp("reboot","");
        sys.exit(0);

x = ButtonChoiceWindow(screen, "Installer", "Press Ok to proceed...")
CheckCancel(x)

screen.finish()
set_tty(3)