def yesno(message, default='yes', suffix=' '):
    """ Prompt user to answer yes or no. Return True if the default is chosen,
     otherwise False. """
    if default == 'yes':
        yesno_prompt = '[Y/n]'
    elif default == 'no':
        yesno_prompt = '[y/N]'
    else:
        raise ValueError("default must be 'yes' or 'no'.")

    if message != '':
        prompt_text = "{0} {1}{2}".format(message, yesno_prompt, suffix)
    else:
        prompt_text = "{0}{1}".format(yesno_prompt, suffix)

    while True:
        response = get_input(prompt_text).strip()
        if response == '':
            return True
        else:
            if re.match('^(y)(es)?$', response, re.IGNORECASE):
                if default == 'yes':
                    return True
                else:
                    return False
            elif re.match('^(n)(o)?$', response, re.IGNORECASE):
                if default == 'no':
                    return True
                else:
                    return False
Prompt user to answer yes or no. Return True if the default is chosen,
     otherwise False.