[mod_python] Rendering a page as a 404?

I'm currently trying to set up my own 404 handler in mod_python, but
haven't had any luck tracking down how I can do that.  My first attempt
was:

   req.send_http_header()
   if pagebuffer: req.write(pagebuffer)
   return(404)

(roughly), but what was happening was that my page was being sent, then
the normal Apache 404 handler was occuring.  The first header sent
was including a 200 status as well.

I've pounded through the documentation and source code and just can't
figure out how I can, effectively, get it to use my content, with a 404
header.

Any thoughts?

Thanks,
Sean
-- 
 The social dynamics of the net are a direct consequence of the fact
 that nobody has yet developed a Remote Strangulation Protocol.
Sean Reifschneider, Member of Technical Staff <jafo at tummy.com>
tummy.com, ltd. - Linux Consulting since 1995.  Qmail, Python, SysAdmin