HTTP Error 400: Bad Request; google app engine + telegram api - http

Question

So i'm working on a telegram bot for a multi-player board game. Web hook is set. And there appears to be a http 400 error when the bot tries to privately message each user in the group chat. What happened to the bot is that it got stuck and keeps messaging one player.
my code:
BASE_URL = 'https://api.telegram.org/bot' + TOKEN + '/'
class WebhookHandler(webapp2.RequestHandler):
def post(self):
urlfetch.set_default_fetch_deadline(60)
body = json.loads(self.request.body)
logging.info('request body:')
logging.info(body)
self.response.write(json.dumps(body))
update_id = body['update_id']
try:
message = body['message']
except:
message = body['edited_message']
message_id = message.get('message_id')
date = message.get('date')
text = message.get('text')
fr = message.get('from')
chat = message['chat']
chat_id = chat['id']
chat_type = chat['type']
fr_user_id = fr['id']
fr_user_name = fr['first_name']
if not text:
logging.info('no text')
return
def reply_to_user(desti_user_id, msg):
if msg:
resp = urllib2.urlopen(BASE_URL + 'sendMessage', urllib.urlencode({
'chat_id': str(desti_user_id),
**#line 115!** 'text': msg.encode('utf-8')
})).read()
else:
logging.error('no msg or img specified')
resp = None
logging.info('send response:')
logging.info (resp)
The LOG(google app engine):
HTTP Error 400: Bad Request (/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py:1552)
Traceback (most recent call last):
File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 1535, in __call__
rv = self.handle_exception(request, response, e)
File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 1529, in __call__
rv = self.router.dispatch(request, response)
File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 1278, in default_dispatcher
return route.handler_adapter(request, response)
File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 1102, in __call__
return handler.dispatch()
File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 572, in dispatch
return self.handle_exception(e, self.app.debug)
File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 570, in dispatch
return method(*args, **kwargs)
File "/base/data/home/apps/s~orbitaltest2/1.394273849972192493/main.py", line 241, in post
reply_to_user(player.user_id, "you are: a member of the resistance")
File "/base/data/home/apps/s~orbitaltest2/1.394273849972192493/main.py", line 115, in reply_to_user
'text': msg.encode('utf-8'),
File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/urllib2.py", line 127, in urlopen
return _opener.open(url, data, timeout)
File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/urllib2.py", line 410, in open
response = meth(req, response)
File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/urllib2.py", line 523, in http_response
'http', request, response, code, msg, hdrs)
File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/urllib2.py", line 448, in error
return self._call_chain(*args)
File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/urllib2.py", line 382, in _call_chain
result = func(*args)
File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/urllib2.py", line 531, in http_error_default
raise HTTPError(req.get_full_url(), code, msg, hdrs, fp)
HTTPError: HTTP Error 400: Bad Request
not sure what happened.