Like os.path.splitext, but take off .tar too

def splitext(path):
    # type: (str) -> Tuple[str, str]
    """Like os.path.splitext, but take off .tar too"""
    base, ext = posixpath.splitext(path)
    if base.lower().endswith('.tar'):
        ext = base[-4:] + ext
        base = base[:-4]
    return base, ext