Fix tempfile.mktemp()

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-03-23.15:26:30.711>
labels = ['type-security', 'library', '3.10']
title = 'Fix tempfile.mktemp()'
updated_at = <Date 2021-03-23.19:35:24.997>
user = 'https://github.com/dlukes'

bugs.python.org fields:

activity = <Date 2021-03-23.19:35:24.997>
actor = 'dlukes'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2021-03-23.15:26:30.711>
creator = 'dlukes'
dependencies = []
files = []
hgrepos = []
issue_num = 43604
keywords = []
message_count = 4.0
messages = ['389393', '389394', '389402', '389407']
nosy_count = 2.0
nosy_names = ['serhiy.storchaka', 'dlukes']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'security'
url = 'https://bugs.python.org/issue43604'
versions = ['Python 3.10']