def clean(self):
        if self.static or not self.published:
            return

        # fields are missing, validating uniqueness is pointless
        if not self.category_id or not self.publish_from or not self.slug:
            return

        qset = self.__class__.objects.filter(
                category=self.category,
                published=True,
                publish_from__day=self.publish_from.day,
                publish_from__month=self.publish_from.month,
                publish_from__year=self.publish_from.year,
                slug=self.slug
            )

        if self.pk:
            qset = qset.exclude(pk=self.pk)

        if qset:
            raise ValidationError(self._meta.verbose_name % _('Another %s already published at this URL.'))
dataset/ETHPy150Open ella/ella/ella/core/models/publishable.py/Publishable.clean/swapped operands of `%`