readline() specification is unclear

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-01-31.18:13:51.211>
labels = ['3.8', 'docs']
title = 'readline() specification is unclear'
updated_at = <Date 2019-01-31.23:28:45.041>
user = 'https://github.com/vporton'

bugs.python.org fields:

activity = <Date 2019-01-31.23:28:45.041>
actor = 'martin.panter'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2019-01-31.18:13:51.211>
creator = 'porton'
dependencies = []
files = []
hgrepos = []
issue_num = 35870
keywords = []
message_count = 2.0
messages = ['334634', '334638']
nosy_count = 3.0
nosy_names = ['docs@python', 'martin.panter', 'porton']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue35870'
versions = ['Python 3.8']