In [this PR](https://github.com/localstack/localstack/pull/1200/files) we introduced a new way of starting S3 in a separate process.

In the meantime, the service startup has been significantly reworked, and it seems that we can integrate the S3 starter into the [`multiserver.py`](https://github.com/localstack/localstack/blob/master/localstack/utils/server/multiserver.py) based loading approach that loads multiple APIs in a single process, for performance reasons. We should look into that.
self.s3_client.create_bucket(Bucket=TEST_BUCKET_NAME_WITH_POLICY)
        
        policy = {
            'Version': '2012-10-17',
            'Statement': {
                'Action': ['s3:GetObject'],
                'Effect': 'Allow',
                'Resource': 'arn:aws:s3:::bucketName/*',
                'Principal': {
                    'AWS': ['*']
                }
            }
        }
        response = self.s3_client.put_bucket_policy(
            Bucket=TEST_BUCKET_NAME_WITH_POLICY,
            Policy=json.dumps(policy)
        )
        self.assertEqual(response['ResponseMetadata']['HTTPStatusCode'], 204)
        
        saved_policy = self.s3_client.get_bucket_policy(Bucket=TEST_BUCKET_NAME_WITH_POLICY)['Policy']
        self.assertEqual(json.loads(saved_policy), policy)
    def test_s3_put_object_notification(self):