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.
prefix = 'MessageAttribute'
        names = []
        for (k, name) in [(k, data[k]) for k in data if k.startswith(prefix) and k.endswith('.Name')]:
            attr_name = name[0]
            k_id = k.split('.')[1]
            names.append((attr_name, k_id))
        msg_attrs = {}
        for (key_name, key_id) in names:
            msg_attrs[key_name] = {}
            
            attrs = [(k, data[k]) for k in data
                if k.startswith('{}.{}.'.format(prefix, key_id)) and not k.endswith('.Name')]
            for (attr_k, attr_v) in attrs:
                attr_name = attr_k.split('.')[3]
                msg_attrs[key_name][attr_name[0].lower() + attr_name[1:]] = attr_v[0]
            
            
            
            msg_attrs[key_name]['stringListValues'] = []
            msg_attrs[key_name]['binaryListValues'] = []
        return msg_attrs
    @classmethod
    def get_message_attributes_md5(self, req_data):