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.
self.assertEqual(content['data'], data)
        self.assertEqual(headers['content-type'], ctype)
        
        proxy.stop()
    def test_api_gateway_lambda_proxy_integration(self):
        self._test_api_gateway_lambda_proxy_integration(
            self.TEST_LAMBDA_PROXY_BACKEND,
            self.API_PATH_LAMBDA_PROXY_BACKEND)
    def test_api_gateway_lambda_proxy_integration_with_path_param(self):
        self._test_api_gateway_lambda_proxy_integration(
            self.TEST_LAMBDA_PROXY_BACKEND_WITH_PATH_PARAM,
            self.API_PATH_LAMBDA_PROXY_BACKEND_WITH_PATH_PARAM)
    def _test_api_gateway_lambda_proxy_integration(self, fn_name, path):
        self.create_lambda_function(fn_name)
        
        lambda_uri = aws_stack.lambda_function_arn(fn_name)
        invocation_uri = 'arn:aws:apigateway:%s:lambda:path/2015-03-31/functions/%s/invocations'
        target_uri = invocation_uri % (config.DEFAULT_REGION, lambda_uri)
        result = self.connect_api_gateway_to_http_with_lambda_proxy(
            'test_gateway2', target_uri, path=path)
        api_id = result['id']
        path_map = get_rest_api_paths(api_id)
        _, resource = get_resource_for_path('/lambda/foo1', path_map)
        
        path = path.replace('{test_param1}', 'foo1')
        path = path + '?foo=foo&bar=bar&bar=baz'
        url = self.gateway_request_url(
            api_id=api_id, stage_name=self.TEST_STAGE_NAME, path=path)
        data = {'return_status_code': 203, 'return_headers': {'foo': 'bar123'}}
        result = requests.post(url, data=json.dumps(data),