def get_file(message, default=None):
    """ Get a reference to a file and make sure it exists

    Returns:
        path: The path to the file, if it exists

    Raises:
        ValueError: If the provided file does not exist
    """
    if default:
        path = input('{} ({}): '.format(message, default))
    else:
        path = input('{}: '.format(message))
    return path
