我有这个django代码，它通过inscode从redis获取数据并返回。如果redis关闭了，它应该跳出try，expect block并从数据库（postgresql）读取数据。

class GetOrderBook(APIView):
    def get(self, request, format=None):
        # get parameters
        inscode = None
        if 'i' in request.GET:
            inscode = request.GET['i']

        if inscode != None:
            try:
                #raise ('disabling redis!')
                r_handle = redisconnection

                data = r_handle.get(inscode)

                if data != None:
                    return Response(200)
                else:
                    print('not found in cache')
            except BaseException as err:
                print(err)
            orderbook = OrderBook.objects.filter(
                symbol__inscode=inscode).order_by('rownum')
            if len(orderbook) > 0:
                data = OrderBookSer(orderbook, many=True).data
                data_formatted = {'buynum': [0]*5, 'buyvol': [0]*5, 'buyprice': [
                    0]*5, 'sellnum': [0]*5, 'sellvol': [0]*5, 'sellprice': [0]*5}
                

                return Response(data_formatted, status=status.HTTP_200_OK)
            else:
                return Response({'Bad Request'}, status.HTTP_404_NOT_FOUND)
        return Response({'Bad Request'}, status.HTTP_400_BAD_REQUEST)

但问题是，它不从数据库阅读，我也写了这个测试，它返回200，如果你读数据。但是当Redis关闭时，它不会读数据，并返回404给我。

def test_redis_function(self, api_client, test_user):
    url = self.url
    api_client.force_authenticate(user=test_user)  
    
    response = api_client.get(url, {'i': '2400322364771558'}) 
    assert response.status_code == status.HTTP_200_OK

如果你能帮我我会很高兴的