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.
for i, m in enumerate(event_source_mappings):
        if uuid_value == m['UUID']:
            return event_source_mappings.pop(i)
    return {}
def use_docker():
    global DO_USE_DOCKER
    if DO_USE_DOCKER is None:
        DO_USE_DOCKER = False
        if 'docker' in config.LAMBDA_EXECUTOR:
            try:
                run('docker images', print_error=False)
                DO_USE_DOCKER = True
            except Exception:
                pass
    return DO_USE_DOCKER
def process_apigateway_invocation(func_arn, path, payload, headers={},
        resource_path=None, method=None, path_params={},
        query_string_params={}, request_context={}):
    try:
        resource_path = resource_path or path
        event = {
            'path': path,
            'headers': dict(headers),
            'pathParameters': dict(path_params),
            'body': payload,
            'isBase64Encoded': False,
            'resource': resource_path,
            'httpMethod': method,