infinite waiting in multiprocessing.Pool

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2018-09-23.20:30:41.727>
labels = ['type-bug']
title = 'infinite waiting in multiprocessing.Pool'
updated_at = <Date 2022-01-27.10:46:22.005>
user = 'https://github.com/coells'

bugs.python.org fields:

activity = <Date 2022-01-27.10:46:22.005>
actor = 'antonio.vazquez'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2018-09-23.20:30:41.727>
creator = 'coells'
dependencies = []
files = []
hgrepos = []
issue_num = 34781
keywords = []
message_count = 11.0
messages = ['326178', '326187', '326401', '326407', '326408', '326448', '326482', '326483', '326484', '326499', '336538']
nosy_count = 9.0
nosy_names = ['ronaldoussoren', 'pitrou', 'ned.deily', 'davin', 'calimeroteknik', 'coells', 'Dongyan Li', 'myles.steinhauser', 'antonio.vazquez']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue34781'
versions = ['Python 2.7', 'Python 3.6']