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.
queue_url, queue_attributes = self._create_test_queue()
        self._create_test_notification_bucket(queue_attributes)
        
        file_size = 75000000
        large_file = self.generate_large_file(file_size)
        download_file = new_tmp_file()
        try:
            self.s3_client.upload_file(Bucket=TEST_BUCKET_WITH_NOTIFICATION,
                                       Key=large_file.name, Filename=large_file.name)
            self.assertEqual(self._get_test_queue_message_count(queue_url), '1')
            
            messages = self.sqs_client.receive_message(QueueUrl=queue_url, AttributeNames=['All'])
            message = json.loads(messages['Messages'][0]['Body'])
            self.assertEqual(message['Records'][0]['eventName'], 'ObjectCreated:CompleteMultipartUpload')
            
            self.s3_client.download_file(Bucket=TEST_BUCKET_WITH_NOTIFICATION,
                                         Key=large_file.name, Filename=download_file)
            self.assertEqual(os.path.getsize(download_file), file_size)
            
            self.sqs_client.delete_queue(QueueUrl=queue_url)
            self._delete_bucket(TEST_BUCKET_WITH_NOTIFICATION, large_file.name)
        finally:
            
            large_file.close()
            rm_rf(large_file.name)
            rm_rf(download_file)
    def test_s3_multipart_upload_with_small_single_part(self):