To avoid too much outside reference, the commit message I am unsure of is this.

> Run Python 3 in unbuffered mode to see lines in `docker logs` as soon as they appear. When Python 3 is not attached to a terminal, it turns on the buffering, like when `docker` runs in a background.

I am not sure.

1. How Python detects it is attached to terminal or not.
2. That it is Python that turns on stdout buffering.
3. What happens to stdout with child processes when they run with docker in different modes - foreground, background (-d), interactive (-i), with tty (-t) and without tty.