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.
return pool[obj]
        inst = None
        if obj.startswith('arn:aws:kinesis:'):
            inst = KinesisStream(obj)
        elif obj.startswith('arn:aws:lambda:'):
            inst = LambdaFunction(obj)
        elif obj.startswith('arn:aws:dynamodb:'):
            if '/stream/' in obj:
                table_id = obj.split('/stream/')[0]
                table = DynamoDB(table_id)
                inst = DynamoDBStream(obj)
                inst.table = table
            else:
                inst = DynamoDB(obj)
        elif obj.startswith('arn:aws:sqs:'):
            inst = SqsQueue(obj)
        elif type:
            for o in EventSource.filter_type(pool, type):
                if o.name() == obj:
                    return o
                if type == ElasticSearch:
                    if o.endpoint == obj:
                        return o
        else:
            print("Unexpected object name: '%s'" % obj)
        return inst
    @staticmethod
    def filter_type(pool, type):
        return [obj for obj in six.itervalues(pool) if isinstance(obj, type)]