Dialog with a process via subprocess.Popen blocks forever

[bayer.justin at googlemail.com]

> If you are both waiting for input, you have a Mexican standoff...

That is not the problem. The problem is, that the buffers are not
flushed correctly. It's a dialogue, so nothing complicated. But python
does not get what the subprocess sends onto the subprocess' standard
out - not every time, anyway.

I'm quite confused, but hopefully will understand what's going on and
come back here.