> Man page of Python says 
> 
>   -u Force  stdin,  stdout  and  stderr to be totally unbuffered.  On
>      systems where it matters, also put stdin, stdout and  stderr  in
>      binary  mode.   

I don't know which version it is, but current 3.3 says:

“Force the binary I/O layers of stdin, stdout and  stderr  to  be
unbuffered.  The text I/O layer will still be line-buffered.”

> test_httpservers depends on this behavior, but was implemented as
> documented in Python 3.

I would argue that test_httpservers is wrong, since it uses print() in a
CGI script where sys.stdout.buffer.write() should really be used.