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.
event = {'timestamp': int(log_time), 'message': line}
            log_events.append(event)
        if not log_events:
            return
        logs_client.put_log_events(
            logGroupName=log_group_name,
            logStreamName=log_stream_name,
            logEvents=log_events
        )
    def run_lambda_executor(self, cmd, event=None, env_vars={}):
        process = run(cmd, asynchronous=True, stderr=subprocess.PIPE, outfile=subprocess.PIPE, env_vars=env_vars,
                      stdin=True)
        result, log_output = process.communicate(input=event)
        try:
            result = to_str(result).strip()
        except Exception:
            pass
        log_output = to_str(log_output).strip()
        return_code = process.returncode
        
        
        
        if isinstance(result, six.string_types) and '\n' in result:
            additional_logs, _, result = result.rpartition('\n')
            log_output += '\n%s' % additional_logs
        if return_code != 0:
            raise Exception('Lambda process returned error status code: %s. Result: %s. Output:\n%s' %
                (return_code, result, log_output))
        return result, log_output
class ContainerInfo: