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(result['StatusCode'], 202)
    def test_ddb_event(self):
        result = self.lambda_client.invoke(
            FunctionName=TEST_LAMBDA_NAME_JAVA, InvocationType='Event',
            Payload=b'{"Records": [{"dynamodb": {"Message": "{}"}}]}')
        self.assertEqual(result['StatusCode'], 202)
    def test_kinesis_invocation(self):
        result = self.lambda_client.invoke(
            FunctionName=TEST_LAMBDA_NAME_JAVA,
            Payload=b'{"Records": [{"Kinesis": {"Data": "data", "PartitionKey": "partition"}}]}')
        result_data = result['Payload'].read()
        self.assertEqual(result['StatusCode'], 200)
        self.assertIn('KinesisEvent', to_str(result_data))
    def test_kinesis_event(self):
        result = self.lambda_client.invoke(
            FunctionName=TEST_LAMBDA_NAME_JAVA, InvocationType='Event',
            Payload=b'{"Records": [{"Kinesis": {"Data": "data", "PartitionKey": "partition"}}]}')
        result_data = result['Payload'].read()
        self.assertEqual(result['StatusCode'], 202)
        self.assertEqual(to_str(result_data).strip(), '')
    def test_stream_handler(self):
        result = self.lambda_client.invoke(
            FunctionName=TEST_LAMBDA_NAME_JAVA_STREAM, Payload=b'{}')
        result_data = result['Payload'].read()
        self.assertEqual(result['StatusCode'], 200)
        self.assertEqual(to_str(result_data).strip(), '{}')
    def test_serializable_input_object(self):
        result = self.lambda_client.invoke(
            FunctionName=TEST_LAMBDA_NAME_JAVA_SERIALIZABLE,
            Payload=b'{"bucket": "test_bucket", "key": "test_key"}')