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
legacy_patterns = re.compile(r'^(.+)\.s3\.?(-external-1)?\.amazonaws\.com(\.[a-z]+)?$')
    
    
    for pattern in [common_pattern, dualstack_pattern, legacy_patterns]:
        match = pattern.match(host)
        if match:
            bucket_name = match.groups()[0]
            break
    
    
    return bucket_name
def handle_notification_request(bucket, method, data):
    response = Response()
    response.status_code = 200
    response._content = ''
    if method == 'GET':
        
        result = '<NotificationConfiguration xmlns="%s">' % XMLNS_S3
        if bucket in S3_NOTIFICATIONS:
            notif = S3_NOTIFICATIONS[bucket]
            for dest in NOTIFICATION_DESTINATION_TYPES:
                if dest in notif:
                    dest_dict = {
                        '%sConfiguration' % dest: {
                            'Id': uuid.uuid4(),
                            dest: notif[dest],
                            'Event': notif['Event'],
                            'Filter': notif['Filter']
                        }
                    }