Remove old deprecated unittest features

[serhiy-storchaka]

BPO	45162
Nosy	@gpshead, @rbtcollins, @ezio-melotti, @voidspace, @serhiy-storchaka
PRs	bpo-45162: Remove many old deprecated unittest features #28268 bpo-45162: Revert "Remove many old deprecated unittest features" #30935

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-09-10.10:15:06.032>
labels = ['deferred-blocker', 'type-bug', 'library', '3.11']
title = 'Remove old deprecated unittest features'
updated_at = <Date 2022-01-27.04:40:24.789>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2022-01-27.04:40:24.789>
actor = 'gregory.p.smith'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2021-09-10.10:15:06.032>
creator = 'serhiy.storchaka'
dependencies = []
files = []
hgrepos = []
issue_num = 45162
keywords = ['patch']
message_count = 4.0
messages = ['401568', '402033', '411808', '411838']
nosy_count = 5.0
nosy_names = ['gregory.p.smith', 'rbcollins', 'ezio.melotti', 'michael.foord', 'serhiy.storchaka']
pr_nums = ['28268', '30935']
priority = 'deferred blocker'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue45162'
versions = ['Python 3.11']

[serhiy-storchaka]

The proposed PR removes the following unittest features:

• "fail*" and "assert*" aliases of TestCase methods.
• Broken from start TestCase method assertDictContainsSubset().
• Ignored TestLoader.loadTestsFromModule() parameter use_load_tests.
• Old alias _TextTestResult of TextTestResult.

Most features were deprecated in 3.2, "fail*" methods in 3.1, assertNotRegexpMatches in 3.5. They were kept mostly for compatibility with 2.7 (although some of them were new in Python 3 and not compatible with 2.7).

Using deprecated assertEquals instead of assertEqual is a common error which we need to fix regularly, so removing deprecated features will not only make the current code clearer, but save as from future errors.

[serhiy-storchaka]

New changeset b0a6ede by Serhiy Storchaka in branch 'main':
bpo-45162: Remove many old deprecated unittest features (GH-28268)
b0a6ede

[gpshead]

Per https://mail.python.org/archives/list/python-dev@python.org/thread/GJTREADEXYAETECE5JDTPYWK4WMTKYGR/ we want to revert this change for 3.11 as it causes adoption pain for little benefit.

To determine if we should proceed with this in 3.12 or future versions, run a stable Python with this change applied on the test suites of external projects to find regressions. (many will have been addressed by then thanks to the work by RedHat)

and remember that those are only open source projects. Peoples internal codebases are full of use of these names and this will prevent upgrading until they take the time to address those.

There are targeted pieces of this change that may make sense to go forward with individually. But it is easier to reason about after a rollback and consider new PRs to move those forward.