Print MSG and a confirmation prompt.

    Waiting for user's confirmation, unless silent '--yes-i-know'
    command line option was used, in which case the function
    returns immediately without printing anything.

def wait_for_user(msg=""):
    """
    Print MSG and a confirmation prompt.

    Waiting for user's confirmation, unless silent '--yes-i-know'
    command line option was used, in which case the function
    returns immediately without printing anything.
    """
    if '--yes-i-know' in sys.argv:
        return
    print(msg)
    try:
        answer = raw_input("Please confirm by typing 'Yes, I know!': ")
    except KeyboardInterrupt:
        print()
        answer = ''
    if answer != 'Yes, I know!':
        sys.stderr.write("ERROR: Aborted.\n")
        sys.exit(1)
    return