Interpreter exit blocks waiting for futures of shut-down ThreadPoolExecutors

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-05-03.09:28:03.892>
labels = ['3.7', '3.8', 'type-bug', 'library']
title = 'Interpreter exit blocks waiting for futures of shut-down ThreadPoolExecutors'
updated_at = <Date 2020-04-15.02:39:49.873>
user = 'https://github.com/hniksic'

bugs.python.org fields:

activity = <Date 2020-04-15.02:39:49.873>
actor = 'aeros'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2019-05-03.09:28:03.892>
creator = 'hniksic'
dependencies = []
files = ['48297']
hgrepos = []
issue_num = 36780
keywords = ['patch']
message_count = 19.0
messages = ['341329', '341515', '341573', '341630', '341734', '341737', '341992', '342259', '342260', '342261', '366372', '366415', '366419', '366421', '366424', '366431', '366437', '366439', '366479']
nosy_count = 6.0
nosy_names = ['bquinlan', 'pitrou', 'hniksic', 'asvetlov', 'torsten', 'aeros']
pr_nums = ['13250']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue36780'
versions = ['Python 3.7', 'Python 3.8']