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.
flags = re.MULTILINE | re.DOTALL
        queue_url = self._queue_url(path, req_data, headers)
        regex = r'(.*<GetQueueAttributesResult>)(.*)(</GetQueueAttributesResult>.*)'
        attrs = re.sub(regex, r'\2', content_str, flags=flags)
        for key, value in QUEUE_ATTRIBUTES.get(queue_url, {}).items():
            if not re.match(r'<Name>\s*%s\s*</Name>' % key, attrs, flags=flags):
                attrs += '<Attribute><Name>%s</Name><Value>%s</Value></Attribute>' % (key, value)
        content_str = (re.sub(regex, r'\1', content_str, flags=flags) +
            attrs + re.sub(regex, r'\3', content_str, flags=flags))
        return content_str
    def _fire_event(self, req_data, response):
        action = req_data.get('Action', [None])[0]
        event_type = None
        queue_url = None
        if action == 'CreateQueue':
            event_type = event_publisher.EVENT_SQS_CREATE_QUEUE
            response_data = xmltodict.parse(response.content)
            if 'CreateQueueResponse' in response_data:
                queue_url = response_data['CreateQueueResponse']['CreateQueueResult']['QueueUrl']
        elif action == 'DeleteQueue':
            event_type = event_publisher.EVENT_SQS_DELETE_QUEUE
            queue_url = req_data.get('QueueUrl', [None])[0]
        if event_type and queue_url:
            event_publisher.fire_event(event_type, payload={'u': event_publisher.get_hash(queue_url)})
    def _queue_url(self, path, req_data, headers):