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.
queue_name = 'queue-%s' % short_uid()
        queue_info = self.client.create_queue(QueueName=queue_name)
        queue_url = queue_info['QueueUrl']
        attributes = {
            'Policy': TEST_POLICY
        }
        self.client.set_queue_attributes(QueueUrl=queue_url, Attributes=attributes)
        attrs = self.client.get_queue_attributes(QueueUrl=queue_url, AttributeNames=['All'])['Attributes']
        self.assertIn('sqs:SendMessage', attrs['Policy'])
        attrs = self.client.get_queue_attributes(QueueUrl=queue_url, AttributeNames=['Policy'])['Attributes']
        self.assertIn('sqs:SendMessage', attrs['Policy'])
        
        self.client.delete_queue(QueueUrl=queue_url)
    def test_dead_letter_queue(self):
        queue_name = 'queue-%s' % short_uid()
        dlq_name = 'queue-%s' % short_uid()
        dlq_info = self.client.create_queue(QueueName=dlq_name)
        dlq_arn = aws_stack.sqs_queue_arn(dlq_name)
        attributes = {'RedrivePolicy': json.dumps({'deadLetterTargetArn': dlq_arn, 'maxReceiveCount': 100})}
        queue_info = self.client.create_queue(QueueName=queue_name, Attributes=attributes)
        queue_url = queue_info['QueueUrl']
        
        self.client.delete_queue(QueueUrl=queue_url)
        self.client.delete_queue(QueueUrl=dlq_info['QueueUrl'])