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.
'receiptHandle': 'MessageReceiptHandle',
                'md5OfBody': md5(message_body),
                'eventSourceARN': queue_arn,
                'eventSource': 'aws:sqs',
                'awsRegion': region_name,
                'messageId': str(uuid.uuid4()),
                'attributes': {
                    'ApproximateFirstReceiveTimestamp': '{}000'.format(int(time.time())),
                    'SenderId': TEST_AWS_ACCOUNT_ID,
                    'ApproximateReceiveCount': '1',
                    'SentTimestamp': '{}000'.format(int(time.time()))
                },
                'messageAttributes': message_attributes,
                'sqs': True,
            }]}
            result = run_lambda(event=event, context={}, func_arn=arn)
            status_code = getattr(result, 'status_code', 200)
            if status_code >= 400:
                LOG.warning('Invoking Lambda %s from SQS message failed (%s): %s' % (arn, status_code, result.data))
            return True
    except Exception as e:
        LOG.warning('Unable to run Lambda function on SQS messages: %s %s' % (e, traceback.format_exc()))
def get_event_sources(func_name=None, source_arn=None):
    result = []
    for m in event_source_mappings:
        if not func_name or (m['FunctionArn'] in [func_name, func_arn(func_name)]):
            if _arn_match(mapped=m['EventSourceArn'], occurred=source_arn):
                result.append(m)
    return result
def _arn_match(mapped, occurred):