Inconsistent Behavior Of futures.ProcessPoolExecutor

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2018-10-02.23:16:54.387>
labels = ['interpreter-core', '3.7']
title = 'Inconsistent Behavior Of futures.ProcessPoolExecutor'
updated_at = <Date 2018-10-03.00:15:28.564>
user = 'https://github.com/TensorTom'

bugs.python.org fields:

activity = <Date 2018-10-03.00:15:28.564>
actor = 'xtreak'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Interpreter Core']
creation = <Date 2018-10-02.23:16:54.387>
creator = 'TensorTom'
dependencies = []
files = ['47843']
hgrepos = []
issue_num = 34877
keywords = []
message_count = 1.0
messages = ['326922']
nosy_count = 2.0
nosy_names = ['xtreak', 'TensorTom']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue34877'
versions = ['Python 3.7']