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.
return long(self.end_key) - long(self.start_key)
    def percent(self):
        return 100.0 * self.length() / float(KinesisShard.MAX_KEY)
    def __str__(self):
        return ('Shard(%s, length=%s, percent=%s, start=%s, end=%s)' %
                (self.id, self.length(), self.percent(), self.start_key,
                    self.end_key))
    @staticmethod
    def sort(shards):
        def compare(x, y):
            s1 = long(x.start_key)
            s2 = long(y.start_key)
            if s1 < s2:
                return -1
            elif s1 > s2:
                return 1
            else:
                return 0
        return sorted(shards, cmp=compare)
    @staticmethod
    def max(shards):
        max_shard = None
        max_length = long(0)
        for s in shards:
            if s.length() > max_length:
                max_shard = s
                max_length = s.length()
        return max_shard
class FirehoseStream(KinesisStream):