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.
""" Generic event forwarder Lambda. """
    
    LOGGER.info('Lambda log message - logging module')
    print('Lambda log message - print function')
    if 'httpMethod' in event:
        
        try:
            body = json.loads(event['body'])
        except Exception:
            body = {}
        body['pathParameters'] = event.get('pathParameters')
        body['requestContext'] = event.get('requestContext')
        body['queryStringParameters'] = event.get('queryStringParameters')
        body['httpMethod'] = event.get('httpMethod')
        status_code = body.get('return_status_code', 200)
        headers = body.get('return_headers', {})
        body = body.get('return_raw_body') or body
        return {
            'body': body,
            'statusCode': status_code,
            'headers': headers
        }
    if 'Records' not in event:
        return {
            'event': event,
            'context': {
                'invoked_function_arn': context.invoked_function_arn,
                'function_version': context.function_version,
                'function_name': context.function_name