How to use the whitenoise.responders.MissingFileError function in whitenoise

def get_file_stats(path, encodings, stat_cache):
        # Primary file has an encoding of None
        files = {None: FileEntry(path, stat_cache)}
        if encodings:
            for encoding, alt_path in encodings.items():
                try:
                    files[encoding] = FileEntry(alt_path, stat_cache)
                except MissingFileError:
                    continue
        return files

def get_static_file(self, path, url, stat_cache=None):
        # Optimization: bail early if file does not exist
        if stat_cache is None and not os.path.exists(path):
            raise MissingFileError(path)
        headers = Headers([])
        self.add_mime_headers(headers, path, url)
        self.add_cache_headers(headers, path, url)
        if self.allow_all_origins:
            headers["Access-Control-Allow-Origin"] = "*"
        if self.add_headers_function:
            self.add_headers_function(headers, path, url)
        return StaticFile(
            path,
            headers.items(),
            stat_cache=stat_cache,
            encodings={"gzip": path + ".gz", "br": path + ".br"},
        )

def stat_regular_file(path, stat_function):
        """
        Wrap `stat_function` to raise appropriate errors if `path` is not a
        regular file
        """
        try:
            stat_result = stat_function(path)
        except KeyError:
            raise MissingFileError(path)
        except OSError as e:
            if e.errno in (errno.ENOENT, errno.ENAMETOOLONG):
                raise MissingFileError(path)
            else:
                raise
        if not stat.S_ISREG(stat_result.st_mode):
            if stat.S_ISDIR(stat_result.st_mode):
                raise IsDirectoryError(u"Path is a directory: {0}".format(path))
            else:
                raise NotARegularFileError(u"Not a regular file: {0}".format(path))
        return stat_result

def find_file(self, url):
        # Optimization: bail early if the URL can never match a file
        if not self.index_file and url.endswith("/"):
            return
        if not self.url_is_canonical(url):
            return
        for path in self.candidate_paths_for_url(url):
            try:
                return self.find_file_at_path(path, url)
            except MissingFileError:
                pass

def find_file_at_path_with_indexes(self, path, url):
        if url.endswith("/"):
            path = os.path.join(path, self.index_file)
            return self.get_static_file(path, url)
        elif url.endswith("/" + self.index_file):
            if os.path.isfile(path):
                return self.redirect(url, url[: -len(self.index_file)])
        else:
            try:
                return self.get_static_file(path, url)
            except IsDirectoryError:
                if os.path.isfile(os.path.join(path, self.index_file)):
                    return self.redirect(url, url + "/")
        raise MissingFileError(path)

def find_file_at_path(self, path, url):
        if self.is_compressed_variant(path):
            raise MissingFileError(path)
        if self.index_file:
            return self.find_file_at_path_with_indexes(path, url)
        else:
            return self.get_static_file(path, url)

headers.append(("Location", quote(location.encode("utf8"))))
        self.response = Response(HTTPStatus.FOUND, headers, None)

    def get_response(self, method, request_headers):
        return self.response


class NotARegularFileError(Exception):
    pass


class MissingFileError(NotARegularFileError):
    pass


class IsDirectoryError(MissingFileError):
    pass


class FileEntry(object):
    def __init__(self, path, stat_cache=None):
        stat_function = os.stat if stat_cache is None else stat_cache.__getitem__
        self.stat = self.stat_regular_file(path, stat_function)
        self.path = path

    @staticmethod
    def stat_regular_file(path, stat_function):
        """
        Wrap `stat_function` to raise appropriate errors if `path` is not a
        regular file
        """
        try: