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.
import json
import base64
import logging
import boto3.dynamodb.types
from io import BytesIO
from localstack.utils.aws import aws_stack
from localstack.utils.common import to_str, to_bytes
TEST_BUCKET_NAME = 'test-bucket'
KINESIS_STREAM_NAME = 'test_stream_1'
MSG_BODY_RAISE_ERROR_FLAG = 'raise_error'
MSG_BODY_MESSAGE_TARGET = 'message_target'
logging.basicConfig(level=logging.INFO)
LOGGER = logging.getLogger(__name__)
LOGGER.setLevel(logging.INFO)
class TypeDeserializer(boto3.dynamodb.types.TypeDeserializer):
    def _deserialize_n(self, value):
        return float(value)
    def _deserialize_b(self, value):
        return value        
def handler(event, context):