The issue explained in 12494 is that the caller doesn't have access to the
subprocess.Popen object. I disagree to not kill the process when an
exception is raised, even KeyboardInterrupt.

I also disagree to say that we kill an "arbitrary" process. IMHO it's part
of the API that the process is killed with SIGKILL on error.

Maybe we need to flag to send SIGTERM on exception and then wait N wait
until the child exited, or send SIGKILL after the timeout. Maybe it's
overkill and such API should be developed in third party modules.

Anyway, not sending any signal on exction is not a good idea. We must read
the exit status to avoid zombi process. It's not a matter of sending a
signal but of reading the exit status.