def normalize_options(options):
    """
    Takes some options that have a mixture of - and _ and returns the
    equivalent options with only '_'.
    """
    normalized_opts = {}
    for k, v in options.items():
        normalized_key = k.replace('-', '_')
        assert normalized_key not in normalized_opts, "The key {0} cannot be normalized".format(k)
        normalized_opts[normalized_key] = v
    return normalized_opts