old_contents: # -*- coding: utf-8 -*-
  from django.contrib.contenttypes.models import ContentType
  from django.db.models.signals import post_save
  from django.dispatch import receiver
  from .tasks import push_new_content
  
  @receiver(post_save)
  def post_save_handler(sender, instance, **kwargs):
      instance_type = ContentType.objects.get_for_model(instance.__class__)
  
      push_new_content.apply_async(countdown=1, kwargs={'instance_type_pk': instance_type.pk,
                                                        'instance_pk': instance.pk})
  
new_contents: # -*- coding: utf-8 -*-
  from django.contrib.contenttypes.models import ContentType
  from django.db.models.signals import post_save
  from django.dispatch import receiver
  from .tasks import push_new_content
  
  @receiver(post_save)
  def post_save_handler(sender, instance, **kwargs):
      if ContentType.objects.exists():
          instance_type = ContentType.objects.get_for_model(instance.__class__)
  
          push_new_content.apply_async(countdown=1, kwargs={'instance_type_pk': instance_type.pk,
                                                            'instance_pk': instance.pk})
  
subject: Fix initial migration until ContentType is available