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.
req_data = clone(req_data)
        orig_types = {}
        for key, entry in dict(req_data).items():
            
            
            
            if key.endswith('DataType'):
                parts = entry[0].split('.')
                if len(parts) > 2:
                    short_type_name = parts[0]
                    full_type_name = req_data[key][0]
                    attr_num = key.split('.')[1]
                    attr_name = req_data['MessageAttribute.%s.Name' % attr_num][0]
                    orig_types[attr_name] = full_type_name
                    req_data[key] = [short_type_name]
                    if full_type_name not in TRANSPORT_TYPE_ENCODINGS:
                        TRANSPORT_TYPE_ENCODINGS[full_type_name] = TRANSPORT_TYPE_ENCODINGS[short_type_name]
        moto_message = Message('dummy_msg_id', 'dummy_body')
        moto_message.message_attributes = parse_message_attributes(req_data)
        for key, data_type in orig_types.items():
            moto_message.message_attributes[key]['data_type'] = data_type
        message_attr_hash = moto_message.attribute_md5
        return message_attr_hash
    
    
    
    
    
    def _format_attributes(self, req_data):