Within a Django Model, how can I prevent a delete based on a particular field?

Question

In the following, I have a Post model. A Post object has a status field that can be 'unpublished' or 'published'.

if status is 'published', I'd like to prevent the object from being deleted, and would like to keep this logic encapsulated in the model itself.

from model_utils import Choices  # from Django-Model-Utils
from model_utils.fields import StatusField


class Post(model.Models)

    STATUS = Choices(
        ('unpublished', _('Unpublished')),
        ('published', _('Published')),
    )

    ...

    status = StatusField(default=STATUS.unpublished)

How can I do this? Overriding the delete method won't work if the objects are being deleted in bulk with a QuerySet. I've read not to use receivers, but I'm not sure why.

Answer 1

This is what I have following @Todor's comment:

In signals.py:

from django.db.models import ProtectedError
from django.db.models.signals import pre_delete
from django.dispatch import receiver

from .models import Post

@receiver(pre_delete, sender=Post, dispatch_uid='post_pre_delete_signal')
def protect_posts(sender, instance, using, **kwargs):
    if instance.status is 'unpublished': 
        pass
    else:  # Any other status types I add later will also be protected
        raise ProtectedError('Only unpublished posts can be deleted.')

I welcome improvements or better answers!