zipfile increase in size

GitHub fields:

assignee = 'https://github.com/serhiy-storchaka'
closed_at = None
created_at = <Date 2016-11-16.21:16:06.828>
labels = ['3.7', 'type-bug', 'library']
title = 'zipfile increase in size'
updated_at = <Date 2016-11-19.09:14:23.144>
user = 'https://github.com/bertjwregeer'

bugs.python.org fields:

activity = <Date 2016-11-19.09:14:23.144>
actor = 'serhiy.storchaka'
assignee = 'serhiy.storchaka'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2016-11-16.21:16:06.828>
creator = 'X-Istence'
dependencies = []
files = []
hgrepos = []
issue_num = 28719
keywords = []
message_count = 6.0
messages = ['280992', '281000', '281001', '281004', '281006', '281212']
nosy_count = 2.0
nosy_names = ['X-Istence', 'serhiy.storchaka']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue28719'
versions = ['Python 3.6', 'Python 3.7']