@classmethod
    def validate(cls, lots):
        super().validate(lots)
        for lot in lots:
            lot.check_description_length()

    def check_description_length(self):
        Warning = Pool().get('res.user.warning')
        if (self.packaging_description
        and len(self.packaging_description) > 20):
            key = '%s@%s' % (self.__name__, self.id)
            if Warning.check(key):
                raise LotPackagingWarning(key, gettext(
                    'preciball.msg_lot_packaging_description_length'))