Missing parenthesis in `platform._sys_version_parser`

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-12-02.14:05:34.827>
labels = ['3.8', 'type-bug', 'library']
title = 'Missing parenthesis in `platform._sys_version_parser`'
updated_at = <Date 2020-12-02.14:05:34.827>
user = 'https://bugs.python.org/crazy95sun'

bugs.python.org fields:

activity = <Date 2020-12-02.14:05:34.827>
actor = 'crazy95sun'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2020-12-02.14:05:34.827>
creator = 'crazy95sun'
dependencies = []
files = []
hgrepos = []
issue_num = 42539
keywords = []
message_count = 1.0
messages = ['382313']
nosy_count = 1.0
nosy_names = ['crazy95sun']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue42539'
versions = ['Python 3.8']