I love `concurrent.futures`, and I'd like to use it wherever I can. There's a feature in `multiprocessing.Pool` that I wish would also be available in `ProcessPoolExecutor`: The `maxtasksperchild` argument.

Documentation: "maxtasksperchild is the number of tasks a worker process can complete before it will exit and be replaced with a fresh worker process, to enable unused resources to be freed. The default maxtasksperchild is None, which means worker processes will live as long as the pool."

I want to be able to set it to 1, so each process will only execute one task and then be replaced with a fresh process.