export the set newline value on TextIOBase/TextIOWrapper

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-02-27.05:45:28.919>
labels = ['type-feature', 'expert-IO']
title = 'export the set newline value on TextIOBase/TextIOWrapper'
updated_at = <Date 2021-03-05.21:03:13.665>
user = 'https://bugs.python.org/calestyo'

bugs.python.org fields:

activity = <Date 2021-03-05.21:03:13.665>
actor = 'terry.reedy'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['IO']
creation = <Date 2021-02-27.05:45:28.919>
creator = 'calestyo'
dependencies = []
files = []
hgrepos = []
issue_num = 43337
keywords = []
message_count = 1.0
messages = ['387767']
nosy_count = 2.0
nosy_names = ['benjamin.peterson', 'calestyo']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue43337'
versions = []