<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_stoplist(language):
 """Returns an built-in stop-list for the language as a set of words."""

    file_path = os.path.join("stoplists", "%s.txt" % language)
    try:
        stopwords = pkgutil.get_data("justext", file_path)
    except IOError:
        raise ValueError(
            "Stoplist for language '%s' is missing. "
            "Please use function 'get_stoplists' for complete list of stoplists "
            "and feel free to contribute by your own stoplist." % language
        )

    return frozenset(w.decode("utf8").lower() for w in stopwords.splitlines())