cannot concatenate 'str' and 'NoneType' objects


Traceback (most recent call last):
  File "/mnt/hd/web/1bpm.net/ml.csound/app/handler.py", line 386, in <module>
    handle()
  File "/mnt/hd/web/1bpm.net/ml.csound/app/handler.py", line 373, in handle
    return Thread(mailing_list).render({"threadid": int(parts[2])})
  File "/mnt/hd/web/1bpm.net/ml.csound/app/handler.py", line 203, in render
    self.create(data)
  File "/mnt/hd/web/1bpm.net/ml.csound/app/handler.py", line 275, in create
    content += msg.html
  File "/mnt/hd/web/1bpm.net/ml.csound/app/handler.py", line 154, in html
    if len(self.article.attachments) > 0:
  File "/mnt/hd/web/1bpm.net/ml.csound/app/handler.py", line 141, in article
    result = get_nntp(self.mailing_list).article(self.messageid)
  File "/usr/lib/python2.7/nntplib.py", line 453, in article
    return self.artcmd('ARTICLE ' + id)
TypeError: cannot concatenate 'str' and 'NoneType' objects