Fixed #23039: Don't try to serialize unmanaged models in tests

        # Make a function to iteratively return every object

        def get_objects():

            for model in sort_dependencies(app_list):

                if not model._meta.proxy and router.allow_migrate(self.connection.alias, model):

                if not model._meta.proxy and model._meta.managed and router.allow_migrate(self.connection.alias, model):

                    queryset = model._default_manager.using(self.connection.alias).order_by(model._meta.pk.name)

                    for obj in queryset.iterator():

                        yield obj

class Book(models.Model):

    title = models.CharField(max_length=100)

class Unmanaged(models.Model):

    title = models.CharField(max_length=100)

    class Meta:

        managed = False