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.
def __init__(self, id):
        super(FirehoseStream, self).__init__(id)
        self.destinations = []
    def name(self):
        return self.id.split(':deliverystream/')[-1]
class LambdaFunction(Component):
    def __init__(self, arn):
        super(LambdaFunction, self).__init__(arn)
        self.event_sources = []
        self.targets = []
        self.versions = {}
        self.aliases = {}
        self.envvars = {}
        self.tags = {}
        self.concurrency = None
        self.runtime = None
        self.handler = None
        self.cwd = None
        self.timeout = None
        self.last_modified = None
        self.description = ''
        self.role = None
        self.memory_size = None
        self.code = None
    def get_version(self, version):