If a process fails during run_multiple_processes() we don't know about it until all processes have finished #44

I've seen this with CRATE. If you launch a multi-process anonymisation and one of the processes fails, it doesn't get reported until all of the processes have completed and the die_on_failure argument has no effect.

The test files multiprocess_test.py and multiprocess.py demonstrate this.

With some debugging of subproc.py, it looks like TimeoutExpired never gets raised in _wait_for_processes().

If I remove this call:

the function works as I would expect. I don't know enough (yet) about the multiprocessing module to know why this is.

This is on Linux.