waitpid_patch.py

import os
from functools import wraps


def waitpid(func):
    cache = {}

    @wraps(func)
    def wrapper(pid, options):
        try:
            wpid, status = func(pid, options)
            if wpid > 0:
                cache[wpid] = status
        except OSError as e:
            if pid in cache:
                return pid, cache[pid]
            else:
                raise e
        else:
            return wpid, status

    return wrapper


os.waitpid = waitpid(os.waitpid)