Hi

I have issues creating sns subscriptions through Cloudformation. If I attempt to include a `AWS::SNS::Subscription` resource in a Cloudformation template and run `create-stack` then I get a 500 Internal Server error. The full template:

```
AWSTemplateFormatVersion: '2010-09-09'
Description: 'Test'
Resources:
  MySnsTopic:
    Type: AWS::SNS::Topic
    Properties:
      TopicName: MySnsTopic
  MySnsTopicSubscription:
    Type: AWS::SNS::Subscription
    Properties:
      Protocol: sqs
      TopicArn: !Ref MySnsTopic
      Endpoint: !GetAtt
        - MySqsQueue
        - QueueArn
  MySqsQueue:
    Type: AWS::SQS::Queue
    Properties:
      QueueName: MySqsQueue
```

If I replace the references with hard-coded arns like this:

```
TopicArn: arn:aws:sns:eu-west-2:123456789012:MySnsTopic
Endpoint: arn:aws:sqs:elasticmq:000000000000:MySqsQueue
```

Then I get no errors but I get a warning:

`No moto Cloudformation support for AWS::SNS::Subscription`.

I can get around this issue by creating the subscription when creating the topic but the issue there is that I cannot add any attributes and in my case I need `RawMessageDelivery` set to true. So my questions are:

1. Is there no support to create `AWS::SNS::Subscription` resources through Cloudformation or am I doing something wrong?
2. If support is not there can I request it as a new feature?
3. Any suggestions on how I can work around this? I know I could do this through a script at startup but would like to not have any additional script steps other than deploying the Cloudformation stack.

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return get_local_region()
def get_local_region():
    global LOCAL_REGION
    if LOCAL_REGION is None:
        session = boto3.session.Session()
        LOCAL_REGION = session.region_name or ''
    return LOCAL_REGION or config.DEFAULT_REGION
def get_local_service_url(service_name_or_port):
    """ Return the local service URL for the given service name or port. """
    if isinstance(service_name_or_port, int):
        return '%s://%s:%s' % (get_service_protocol(), LOCALHOST, service_name_or_port)
    service_name = service_name_or_port
    if service_name == 's3api':
        service_name = 's3'
    return os.environ['TEST_%s_URL' % (service_name.upper().replace('-', '_'))]
def is_service_enabled(service_name):
    """ Return whether the service with the given name (e.g., "lambda") is available. """
    try:
        url = get_local_service_url(service_name)
        assert url
        return is_port_open(url, http_path='/', expect_success=False)
    except Exception:
        return False
def connect_to_service(service_name, client=True, env=None, region_name=None, endpoint_url=None, config=None):