Include thread_name_prefix in the concurrent.futures.ThreadPoolExecutor example 17.4.2.1

GitHub fields:

assignee = 'https://github.com/Mariatta'
closed_at = None
created_at = <Date 2017-01-16.16:42:44.559>
labels = ['3.8', 'type-feature', '3.7', 'docs']
title = 'Include thread_name_prefix  in the concurrent.futures.ThreadPoolExecutor example 17.4.2.1'
updated_at = <Date 2019-04-10.12:08:39.841>
user = 'https://github.com/jftuga'

bugs.python.org fields:

activity = <Date 2019-04-10.12:08:39.841>
actor = 'cheryl.sabella'
assignee = 'Mariatta'
closed = False
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2017-01-16.16:42:44.559>
creator = 'jftuga'
dependencies = []
files = ['46377']
hgrepos = []
issue_num = 29284
keywords = []
message_count = 6.0
messages = ['285572', '286006', '291605', '298733', '298748', '339854']
nosy_count = 6.0
nosy_names = ['gregory.p.smith', 'docs@python', 'jftuga', 'davin', 'Mariatta', 'cheryl.sabella']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue29284'
versions = ['Python 3.7', 'Python 3.8']