Return a list of (lower-cased) names if available (unloaded) Packs.

def get_available_pack_names():
    """Return a list of (lower-cased) names if available (unloaded) Packs.
    """
    installed_pack_names = [pack.name.lower() for pack in Pack.objects.all()]
    fortunes_path = get_fortunes_path()
    for path in fortunes_path.iterdir():
        if path.is_dir():
            pass
        elif path.suffix == ".dat":
            pass
        elif path.name.lower() in installed_pack_names:
            pass
        else:
            yield path.name.lower()