Return the innings file of a game with matching id.

def get_innings(game_id):
    """Return the innings file of a game with matching id."""
    year, month, day = get_date_from_game_id(game_id)
    try:
        return urlopen(INNINGS_URL.format(year, month, day, game_id))
    except HTTPError:
        raise ValueError('Could not find a game with that id.')