TypeError：无法解压缩不可迭代的NoneType对象->但是对象存在吗？

Question

我为某些代码而生气。执行随机生成产品建议的程序总是会导致错误

  

TypeError：无法解包不可迭代的NoneType对象

但我似乎看不到返回NoneType对象的位置。所有打印语句均清楚表明我返回了一个对象和一个布尔值。不幸的是，这是很多代码，而且我似乎无法用更少的代码来重现错误。

@staticmethod
def generate_random_product(variation):
    product_options = Product.objects.all()
    if not product_options:
        raise ValidationError(
            'PRODUCT CREATION FAILED HARD COULD NOT '
            'GENERATE RANDOM PRODUCT FOR: '
            + variation.name + '... PLEASE DELETE'
            'ALL DELIVERIES THAT WERE CREATED TODAY'
        )
    random_int = random.randint(0, (product_options.count() - 1))
    return product_options[random_int], True

def generate_random_product_from_category(self, variation, count):
    if count >= 10:
        return self.generate_random_product(variation, count)
    category = variation.package.category
    product_options = category.product_set.all()
    if not product_options:
        return self.generate_random_product(variation)
    random_int = random.randint(0, (product_options.count() - 1))
    return product_options[random_int], True

def generate_random_product_from_variation(self, variation, count):
    if count >= 5:
        return self.generate_random_product_from_category(variation, count)
    product_options = variation.product_set.all()
    if not product_options:
        return self.generate_random_product_from_category(variation)
    random_int = random.randint(0, (product_options.count() - 1))
    return product_options[random_int], False

def turn_variation_into_product(self, variation, delivery, count):
    if count < 15:
        # STEP 1: generate a random product
        random_product, failed_auto = self.generate_random_product_from_variation(variation, count)
        print(random_product)
        try:
            self.turn_variation_into_product(variation, delivery, count + 1)
        except (DeliveryItem.DoesNotExist) as e:
            print('return')
            print(random_product, failed_auto)
            return random_product, failed_auto
    else:
        delivery.delete()
        raise ValidationError(
            f'all options for {variation.name} are already '
            f'included in delivery {delivery.slug} ... tried '
            f'*{count}* times')


def create_delivery_items(self, delivery):
    schema_items = delivery.delivery_schema.schemaitem_set.all()
    for schema_item in schema_items:
        if schema_item.variation and not schema_item.product:
            random_product, failed_auto = self.turn_variation_into_product(schema_item.variation, delivery, 0)
            DeliveryItem.objects.create(
                quantity=schema_item.quantity,
                variation=schema_item.variation,
                product=random_product,
                original_type=schema_item.type,
                delivery=delivery,
                failed_auto=failed_auto,
            )

此行导致错误：

  

random_product，failed_auto = self.turn_variation_into_product（schema_item.variation，delivery，0）

如您所见，我在相关return语句的正上方有print语句。但是print语句会输出正确的对象。