looks like setting ExposeHeaders has no effect on requests to s3 (headers such as `x-amz-version-id` don't reach the clients) for browser-based uploads. 

http://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectPOST.html
key_by_path = 'key-by-hostname'
        key_by_host = 'key-by-host'
        
        queue_url = self.sqs_client.create_queue(QueueName=TEST_QUEUE_FOR_BUCKET_WITH_NOTIFICATION)['QueueUrl']
        queue_attributes = self.sqs_client.get_queue_attributes(QueueUrl=queue_url, AttributeNames=['QueueArn'])
        
        self.s3_client.create_bucket(Bucket=TEST_BUCKET_WITH_NOTIFICATION)
        self.s3_client.put_bucket_notification_configuration(Bucket=TEST_BUCKET_WITH_NOTIFICATION,
                                                        NotificationConfiguration={'QueueConfigurations': [
                                                            {'QueueArn': queue_attributes['Attributes']['QueueArn'],
                                                             'Events': ['s3:ObjectCreated:*']}]})
        
        self.s3_client.put_object(Bucket=TEST_BUCKET_WITH_NOTIFICATION, Key=key_by_path, Body='something')
        
        
        headers = {'Host': '{}.s3.amazonaws.com'.format(TEST_BUCKET_WITH_NOTIFICATION), 'authorization': 'some_token'}
        url = '{}/{}'.format(os.getenv('TEST_S3_URL'), key_by_host)