test___all__ and test_distutils alters the enviroinment: pkg_resources.PEP440Warning

[vstinner]

BPO	40055
Nosy	@vstinner, @merwok, @dstufft, @miss-islington
PRs	bpo-40055: distutils tests now disable docutils import #19139 bpo-40055: Fix warnings filters in test_distutils #20095 [3.8] bpo-40055: test_distutils leaves warnings filters unchanged (GH-20095) #20109 [3.7] bpo-40055: test_distutils leaves warnings filters unchanged (GH-20095) #20110

^{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 = <Date 2020-05-16.09:39:36.483>
created_at = <Date 2020-03-24.16:51:30.783>
labels = ['tests', '3.8', '3.7', 'library', '3.9']
title = 'test___all__ and test_distutils alters the enviroinment: pkg_resources.PEP440Warning'
updated_at = <Date 2020-05-16.09:39:36.483>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2020-05-16.09:39:36.483>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2020-05-16.09:39:36.483>
closer = 'vstinner'
components = ['Distutils', 'Tests']
creation = <Date 2020-03-24.16:51:30.783>
creator = 'vstinner'
dependencies = []
files = []
hgrepos = []
issue_num = 40055
keywords = ['patch']
message_count = 5.0
messages = ['364941', '364942', '368954', '368955', '368956']
nosy_count = 4.0
nosy_names = ['vstinner', 'eric.araujo', 'dstufft', 'miss-islington']
pr_nums = ['19139', '20095', '20109', '20110']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue40055'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9']

[vstinner]

Even when no test is run, test_distutils alters the environment:

$ ./python -m test -v --fail-env-changed test_distutils -m DONTEXISTS
== CPython 3.7.7+ (heads/3.7:1cdc61c767, Mar 24 2020, 17:25:30) [GCC 9.2.1 20190827 (Red Hat 9.2.1-1)]
== Linux-5.5.9-200.fc31.x86_64-x86_64-with-fedora-31-Thirty_One little-endian
== cwd: /home/vstinner/python/3.7/build/test_python_157151
== CPU count: 8
== encodings: locale=UTF-8, FS=utf-8
0:00:00 load avg: 0.37 Run tests sequentially
0:00:00 load avg: 0.37 [1/1] test_distutils

---

Ran 0 tests in 0.001s

OK
Warning -- warnings.filters was modified by test_distutils
Before: (140048876788832, [], [])
After: (140048876788832, [], [('ignore', None, <class 'pkg_resources.PEP440Warning'>, None, 0)])
test_distutils run no tests

== Tests result: NO TEST RUN ==

1 test run no tests:
test_distutils

Total duration: 655 ms
Tests result: NO TEST RUN

The problem comes from Lib/distutils/tests/test_check.py: "from distutils.command.check import check, HAS_DOCUTILS" imports indirectly the docutils module which imports pkg_resources.

pkg_resources changes warnings filters.

docutils is installed by python3-docutils-0.15.2-1.fc31.noarch package and pkg_resources comes from python3-setuptools-41.6.0-1.fc31.noarch package.

Attached PR disables docutils to avoid side effects of "import docutils" like pkg_resources modifying warnings filters.

[vstinner]

pkg_resources comes from python3-setuptools-41.6.0-1.fc31.noarch package.

Here is the line which alters warnings filters:

$ grep warnings /usr/lib/python3.7/site-packages/pkg_resources/__init__.py
(...)
warnings.filterwarnings("ignore", category=PEP440Warning, append=True)

[vstinner]

New changeset 6e57237 by Victor Stinner in branch 'master':
bpo-40055: test_distutils leaves warnings filters unchanged (GH-20095)
6e57237

[miss-islington]

New changeset 7ef2751 by Miss Islington (bot) in branch '3.7':
bpo-40055: test_distutils leaves warnings filters unchanged (GH-20095)
7ef2751

[miss-islington]

New changeset 4e6545b by Miss Islington (bot) in branch '3.8':
bpo-40055: test_distutils leaves warnings filters unchanged (GH-20095)
4e6545b