May be a duplicate of https://github.com/localstack/localstack/issues/988 but due to the age I will re raise.

I'm having issues when I throw an exception in a lambda - it isn't appearing on my dead letter queue. Is there something I am missing, I would like an sqs event exception to appear on the poison queue when an exception happens.

Below is the basic config:
 ````
    sqsclient.create_queue(QueueName = 'test-queue')
    sqsclient.create_queue(QueueName = 'test-queue-poison')

    lambda_client.create_function(
            FunctionName='MyFunction',
            Runtime='dotnetcore2.1',
            Role='role',
            Handler='Handler',
            Code=code,
	    DeadLetterConfig={'TargetArn': 'test-queue-poison-arn'})

     lambda_client.create_event_source_mapping(
		EventSourceArn='test-queue-arn',
		FunctionName='MyFunction',
		Enabled=True,
		BatchSize=100,
		StartingPosition='LATEST')
````

So when I raise a new (.net)exception within the lambda function no message is going to the dead letter queue. I can confirm that all is attached together OK as all other scenarios work, and the above code is pseudo-ish.
def test_api_gateway_sqs_integration_with_event_source(self):
        
        aws_stack.create_sqs_queue(self.TEST_SQS_QUEUE)
        
        result = connect_api_gateway_to_sqs(
            'test_gateway4',
            stage_name=self.TEST_STAGE_NAME,
            queue_arn=self.TEST_SQS_QUEUE, path=self.API_PATH_DATA_INBOUND)
        
        self.create_lambda_function(self.TEST_LAMBDA_SQS_HANDLER_NAME)
        add_event_source(
            self.TEST_LAMBDA_SQS_HANDLER_NAME,
            aws_stack.sqs_queue_arn(self.TEST_SQS_QUEUE),
            True)
        
        test_data = {'spam': 'eggs & beans'}
        url = self.gateway_request_url(
            api_id=result['id'],
            stage_name=self.TEST_STAGE_NAME,
            path=self.API_PATH_DATA_INBOUND
        )
        result = requests.post(url, data=json.dumps(test_data))
        self.assertEqual(result.status_code, 200)
        parsed_content = parseString(result.content)
        root = parsed_content.documentElement.childNodes[1]
        attr_md5 = root.childNodes[1].lastChild.nodeValue
        body_md5 = root.childNodes[3].lastChild.nodeValue
        self.assertEqual(attr_md5, 'd41d8cd98f00b204e9800998ecf8427e')
        self.assertEqual(body_md5, 'b639f52308afd65866c86f274c59033f')
    def test_api_gateway_sqs_integration(self):