Never return base's fragment from urljoin (urllib.parse)

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-02-29.15:04:08.115>
labels = ['type-bug', 'library', '3.9']
title = "Never return base's fragment from urljoin (urllib.parse)"
updated_at = <Date 2020-02-29.20:02:49.256>
user = 'https://github.com/openandclose'

bugs.python.org fields:

activity = <Date 2020-02-29.20:02:49.256>
actor = 'op368'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2020-02-29.15:04:08.115>
creator = 'op368'
dependencies = []
files = ['48935']
hgrepos = []
issue_num = 39799
keywords = ['patch']
message_count = 2.0
messages = ['362983', '362984']
nosy_count = 1.0
nosy_names = ['op368']
pr_nums = ['18710']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue39799'
versions = ['Python 3.9']