Ensure backwards compatibility with recommended packages

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2017-10-30.05:23:17.468>
labels = ['3.7', '3.8', 'type-feature', 'tests']
title = 'Ensure backwards compatibility with recommended packages'
updated_at = <Date 2020-06-28.07:17:27.745>
user = 'https://github.com/ncoghlan'

bugs.python.org fields:

activity = <Date 2020-06-28.07:17:27.745>
actor = 'ncoghlan'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Tests']
creation = <Date 2017-10-30.05:23:17.468>
creator = 'ncoghlan'
dependencies = []
files = []
hgrepos = []
issue_num = 31899
keywords = []
message_count = 2.0
messages = ['305211', '372502']
nosy_count = 1.0
nosy_names = ['ncoghlan']
pr_nums = []
priority = 'low'
resolution = None
stage = 'test needed'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue31899'
versions = ['Python 3.7', 'Python 3.8']