Уведомление Django об ошибке для другой модели

Question

Следующий код работает для раздела комментариев.

from django.db import models
from django.contrib.sites.models import Site
from django.db.models import signals
from notification import models as notification

def new_comment(sender, instance, created, **kwargs):
    # remove this if-block if you want notifications for comment edit too
    if not created:
        return None

    context = {
        'comment': instance,
        'site': Site.objects.get_current(),
    }
    recipients = []

    # add all users who commented the same object to recipients
    for comment in instance.__class__.objects.for_model(instance.content_object):
        if comment.user not in recipients and comment.user != instance.user:
            recipients.append(comment.user)

    # if the commented object is a user then notify him as well
    if isinstance(instance.content_object, models.get_model('auth', 'User')):
        # if he his the one who posts the comment then don't add him to recipients
        if instance.content_object != instance.user and instance.content_object not in recipients:
            recipients.append(instance.content_object)

    notification.send(recipients, 'friends_invite', context)

signals.post_save.connect(new_comment, sender=models.get_model('comments', 'Comment'))

Но когда мы реализуем тот же код для другого обычного комментария модели, он дает ошибку во время ввода записи в модель.

from django.db import models
from django.contrib.sites.models import Site
from django.db.models import signals
from notification import models as notification

def create_notice_types(app, created_models, verbosity, **kwargs):
        notification.create_notice_type("friends_invite", _("Invitation Received"), _("you have received an invitation"))
        notification.create_notice_type("friends_accept", _("Acceptance Received"), _("an invitation you sent has been accepted"))

signals.post_syncdb.connect(create_notice_types, sender=notification)

    def new_comment(sender, instance, created, **kwargs):
        # remove this if-block if you want notifications for comment edit too
        if not created:
            return None

        context = {
            'gufeed_feedcomment': instance,
        }
        recipients = []

        # add all users who commented the same object to recipients
        for comment in instance.__class__.objects.for_model(instance.content_object):
            if comment.user not in recipients and comment.user != instance.user:
                recipients.append(comment.user)

        # if the commented object is a user then notify him as well
        if isinstance(instance.content_object, models.get_model('auth', 'User')):
            # if he his the one who posts the comment then don't add him to recipients
            if instance.content_object != instance.user and instance.content_object not in recipients:
                recipients.append(instance.content_object)

        notification.send(recipients, 'friends_invite', context)

    signals.post_save.connect(new_comment, sender=models.get_model('gufeed_feedcomment', 'FeedHottPoint'))

Примечание: мы принимаем тип уведомления friends_invite, он уже создан

ОШИБКА: AttributeError в /gufeed/comment/add/ 'Manager' не имеет атрибута for_model