multiprocessing AuthenticationError when nesting with non-default authkey

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2018-08-31.22:16:52.046>
labels = ['library']
title = 'multiprocessing AuthenticationError when nesting with non-default authkey'
updated_at = <Date 2018-09-20.10:52:33.540>
user = 'https://github.com/natedogith1'

bugs.python.org fields:

activity = <Date 2018-09-20.10:52:33.540>
actor = 'xtreak'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2018-08-31.22:16:52.046>
creator = 'natedogith1'
dependencies = []
files = []
hgrepos = []
issue_num = 34559
keywords = []
message_count = 1.0
messages = ['324447']
nosy_count = 2.0
nosy_names = ['xtreak', 'natedogith1']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue34559'
versions = ['Python 3.6']