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.
docker_cmd = self._docker_cmd()
            status = self.get_docker_container_status(func_arn)
            LOG.debug('Priming docker container (status "%s"): %s' % (status, container_name))
            docker_image = Util.docker_image_for_runtime(runtime)
            rm_flag = Util.get_docker_remove_flag()
            
            if status < 1:
                
                self.destroy_docker_container(func_arn)
                env_vars_str = ' '.join(['-e {}={}'.format(k, cmd_quote(v)) for (k, v) in env_vars])
                network = config.LAMBDA_DOCKER_NETWORK
                network_str = '--network="%s"' % network if network else ''
                mount_volume = not config.LAMBDA_REMOTE_DOCKER
                lambda_cwd_on_host = Util.get_host_path_for_path_in_docker(lambda_cwd)
                mount_volume_str = '-v "%s":/var/task' % lambda_cwd_on_host if mount_volume else ''
                
                LOG.debug('Creating container: %s' % container_name)
                cmd = (
                    '%s create'
                    ' %s'  
                    ' --name "%s"'
                    ' --entrypoint /bin/bash'  
                    ' %s'
                    ' --interactive'  
                    ' -e AWS_LAMBDA_EVENT_BODY="$AWS_LAMBDA_EVENT_BODY"'
                    ' -e HOSTNAME="$HOSTNAME"'
                    ' -e LOCALSTACK_HOSTNAME="$LOCALSTACK_HOSTNAME"'
                    '  %s'  
                    '  %s'  
                    ' %s'