[web2py] Can't send tweet from my application

[Yannick]

Hello Mate,
I used to send tweet through my application successfully without any
trouble but today I keep getting an "401: Unauthorized" when I send a
tweet from my application... Here is the code :
def postTweets():
   try:
        import urllib, urllib2, base64
        import gluon.contrib.simplejson as sj
        args= urllib.urlencode([('status',"My Message")])
        headers={}
        headers['Authorization'] = 'Basic
'+base64.b64encode("userName"+':' +"password")
        request = urllib2.Request('http://twitter.com/statuses/
update.json', args, headers)
        return sj.loads(urllib2.urlopen(request).read())
    except Exception:
        print 'Problem here'
        raise

Here is the error I'm getting:
.....
....
File "/System/Library/Frameworks/Python.framework/Versions/2.5/lib/
python2.5/urllib2.py", line 506, in http_error_default
    raise HTTPError(req.get_full_url(), code, msg, hdrs, fp)
urllib2.HTTPError: HTTP Error 401: Unauthorized



Please any help... thanks