test.py

import os

from multiprocessing import get_context
from concurrent.futures import ProcessPoolExecutor
from concurrent.futures.thread import _global_shutdown_lock as L

os.register_at_fork(
    before=L.acquire,
    after_in_child=L._at_fork_reinit,
    after_in_parent=L.release
)

with ProcessPoolExecutor(mp_context=get_context('fork')) as pool:
    r = list(pool.map(str, range(100)))