Gets URLs to changelogs.
    :param session: requests Session instance
    :param name: str, package name
    :param data: dict, meta data
    :param find_changelogs_fn: function, find_changelogs
    :return: tuple, (set(changelog URLs), set(repo URLs))

def get_urls(session, name, data, find_changelogs_fn, **kwargs):
    """
    Gets URLs to changelogs.
    :param session: requests Session instance
    :param name: str, package name
    :param data: dict, meta data
    :param find_changelogs_fn: function, find_changelogs
    :return: tuple, (set(changelog URLs), set(repo URLs))
    """
    # check if there's a changelog in ../custom/pypi/map.txt
    map = get_url_map()
    if name.lower().replace("_", "-") in map:
        logger.info("Package {name}'s URL is in pypi/map.txt, returning".format(name=name))
        return [map[name.lower().replace("_", "-")]], set()
    # if this package has valid meta data, build up a list of URL candidates we can possibly
    # search for changelogs on
    if "info" in data:
        # add all URLs in pypi's meta data:
        # {
        #   "info": {
        #       "home_page":
        #       "docs_url":
        #       "bugtrack_url":
        #   }
        # }
        candidates = [
            url for url in
            [data["info"].get(attr) for attr in ("home_page", "docs_url", "bugtrack_url")]
            if url
        ]
        # the latest release page on pypi might also contain links, add it
        candidates.append("https://pypi.python.org/pypi/{name}/{latest_release}".format(
            name=name,
            latest_release=next(iter(get_releases(data)))
        ))
        # Check the download URL as well.
        if "download_url" in data:
            candidates.append(data["download_url"])
        if data['info']['description']:
            candidates.extend(changelogs.url_re.findall(data["info"]["description"]))
        return find_changelogs_fn(session=session, name=name, candidates=candidates)
    return set(), set()