def query_yes_no(question, default='no'):
    """
    (From https://gist.github.com/hrouault/1358474)
    Ask a yes/no question via raw_input() and return their answer.

    "question" is a string that is presented to the user.
    "default" is the presumed answer if the user just hits <Enter>.
        It must be "yes" (the default), "no" or None (meaning
        an answer is required of the user).

    The "answer" return value is True for "yes" or False for "no".
    """
    valid = {'yes': True, 'y': True, 'ye': True, 'no': False, 'n': False}
    if default is None:
        prompt = ' [y/n] '
    elif default == 'yes':
        prompt = ' [Y/n] '
    elif default == 'no':
        prompt = ' [y/N] '
    else:
        raise ValueError("invalid default answer: '%s'" % default)
    while True:
        print(question + prompt)
        choice = input().lower()
        if default and choice == '':
            return valid[default]
        elif choice in valid:
            return valid[choice]
        else:
            print("Please respond with 'yes' or 'no' (or 'y' or 'n').\n")
