Workaround for FeinCMS bug, where objects cannot be deleted if there are content types linking to it (IntegrityError)

feincms_delete_fix.py

# Workaround for: https://github.com/feincms/feincms/issues/323
# "Unable to delete pages containing custom content types"

from django.db.models.signals import pre_delete

import logging
log = logging.getLogger(__name__)

def fix_content_model_delete(model):
    """Register a pre-delete handler that will remove all content when a
    content holder is deleted. This prevents a referential integrity error
    when deleting the content holder in MySQL.

    :param model: content type holder inheriting from a FeinCMS Base class
    :type model: feincms.models.Base
    """
    if not hasattr(model, '_feincms_content_types'):
        raise TypeError("Not a FeinCMS Base type model: {0!r}".format(model))

    def handler(sender, instance, **kwargs):
        log.info('pre_delete signal for %r', instance)
        for ct in model._feincms_content_types:
            log.info('deleting: %r references to %r', ct, instance)
            # Delete all content for the instance to be deleted
            ct.objects.filter(parent=instance).delete()

    # weak=False, because the handler will go out-of-scope
    pre_delete.connect(handler, sender=model, weak=False)