状态网，urllib.error.HTTPError：HTTP错误401：未经授权

Question

这是我的代码：

#!/usr/bin/python3
import urllib.request
import urllib.parse

def send_to_statusnet():
    msg = ":)"
    password_manager = urllib.request.HTTPPasswordMgr()
    password_manager.add_password("T2S",
    "http://quitter.se/api/", "USER", "PASS")
    http_handler = urllib.request.HTTPBasicAuthHandler(password_manager)
    page_opener = urllib.request.build_opener(http_handler)
    urllib.request.install_opener(page_opener)
    params = urllib.parse.urlencode( {'status': msg} )
    params = params.encode('utf-8')
    resp = urllib.request.urlopen("http://quitter.se/api/statuses/update.json", params)
    resp.read()

send_to_statusnet()

当我执行此代码时，出现错误：

  File "/usr/lib64/python3.3/urllib/request.py", line 595, in http_error_default
    raise HTTPError(req.full_url, code, msg, hdrs, fp)
urllib.error.HTTPError: HTTP Error 401: Unauthorized

我的代码可能有什么问题？