make shutil.make_archive always accept pathlib objects

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-08-26.10:55:12.392>
labels = ['3.7', '3.8', 'type-bug', 'library']
title = 'make shutil.make_archive always accept pathlib objects'
updated_at = <Date 2020-08-26.11:09:29.339>
user = 'https://github.com/graingert'

bugs.python.org fields:

activity = <Date 2020-08-26.11:09:29.339>
actor = 'graingert'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2020-08-26.10:55:12.392>
creator = 'graingert'
dependencies = []
files = []
hgrepos = []
issue_num = 41643
keywords = ['patch']
message_count = 1.0
messages = ['375927']
nosy_count = 1.0
nosy_names = ['graingert']
pr_nums = ['21962']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue41643'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8']