Refactor zipfile to ease subclassing and enhancement

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-07-10.06:58:30.304>
labels = ['type-feature', 'library', '3.9']
title = 'Refactor zipfile to ease subclassing and enhancement'
updated_at = <Date 2019-07-26.09:26:37.550>
user = 'https://github.com/danifus'

bugs.python.org fields:

activity = <Date 2019-07-26.09:26:37.550>
actor = 'dhillier'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2019-07-10.06:58:30.304>
creator = 'dhillier'
dependencies = []
files = []
hgrepos = []
issue_num = 37538
keywords = ['patch']
message_count = 4.0
messages = ['347604', '347609', '347613', '347972']
nosy_count = 2.0
nosy_names = ['serhiy.storchaka', 'dhillier']
pr_nums = ['14957']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue37538'
versions = ['Python 3.9']