See if this slug exists already

def _clean_page_unique_slug_required(self, slug):
        """See if this slug exists already"""

        if hasattr(self, 'instance') and self.instance.id:
            if Content.objects.exclude(page=self.instance).filter(
                    body=slug, type="slug").count():
                raise forms.ValidationError(self.err_dict['another_page_error'])
        elif Content.objects.filter(body=slug, type="slug").count():
            raise forms.ValidationError(self.err_dict['another_page_error'])
        return slug