lzma: stream padding in xz files

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-05-14.17:52:02.842>
labels = ['type-bug', '3.8', '3.9', '3.10', '3.11', '3.7', 'library']
title = 'lzma: stream padding in xz files'
updated_at = <Date 2021-05-16.10:27:53.156>
user = 'https://github.com/rogdham'

bugs.python.org fields:

activity = <Date 2021-05-16.10:27:53.156>
actor = 'rogdham'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2021-05-14.17:52:02.842>
creator = 'rogdham'
dependencies = []
files = ['50044', '50045']
hgrepos = []
issue_num = 44134
keywords = []
message_count = 2.0
messages = ['393681', '393738']
nosy_count = 3.0
nosy_names = ['nadeem.vawda', 'malin', 'rogdham']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue44134'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8', 'Python 3.9', 'Python 3.10', 'Python 3.11']