gh-109469: Silence compiler warnings on string comparisons in _testcapi

[serhiy-storchaka]

• Issue: Compiler warnings on string comparisons in _testcapi #109469

[miss-islington]

Thanks @serhiy-storchaka for the PR 🌮🎉.. I'm working now to backport this PR to: 3.12.
🐍🍒⛏🤖

[bedevere-app]

GH-109558 is a backport of this pull request to the 3.12 branch.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 RHEL7 3.x has failed when building commit ed582a2.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/15/builds/5695) and take a look at the build logs.
4. Check if the failure is related to this commit (ed582a2) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/15/builds/5695

Failed tests:

• test.test_asyncio.test_subprocess

Failed subtests:

• test_subprocess_consistent_callbacks - test.test_asyncio.test_subprocess.SubprocessThreadedWatcherTests.test_subprocess_consistent_callbacks

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "/home/buildbot/buildarea/3.x.cstratak-RHEL7-x86_64/build/Lib/test/test_asyncio/test_subprocess.py", line 788, in test_subprocess_consistent_callbacks
    self.loop.run_until_complete(main())
  File "/home/buildbot/buildarea/3.x.cstratak-RHEL7-x86_64/build/Lib/asyncio/base_events.py", line 664, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "/home/buildbot/buildarea/3.x.cstratak-RHEL7-x86_64/build/Lib/test/test_asyncio/test_subprocess.py", line 780, in main
    self.assertEqual(events, [
AssertionError: Lists differ: [('pi[29 chars]t'), 'pipe_connection_lost', ('pipe_data_recei[57 chars]ted'] != [('pi[29 chars]t'), ('pipe_data_received', 2, b'stderr'), 'pi[57 chars]ted']

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot aarch64 RHEL8 LTO 3.x has failed when building commit ed582a2.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/338/builds/5102) and take a look at the build logs.
4. Check if the failure is related to this commit (ed582a2) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/338/builds/5102

Failed tests:

• test.test_asyncio.test_subprocess

Failed subtests:

• test_subprocess_consistent_callbacks - test.test_asyncio.test_subprocess.SubprocessFastWatcherTests.test_subprocess_consistent_callbacks

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "/home/buildbot/buildarea/3.x.cstratak-RHEL8-aarch64.lto/build/Lib/test/test_asyncio/test_subprocess.py", line 788, in test_subprocess_consistent_callbacks
    self.loop.run_until_complete(main())
  File "/home/buildbot/buildarea/3.x.cstratak-RHEL8-aarch64.lto/build/Lib/asyncio/base_events.py", line 664, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "/home/buildbot/buildarea/3.x.cstratak-RHEL8-aarch64.lto/build/Lib/test/test_asyncio/test_subprocess.py", line 780, in main
    self.assertEqual(events, [
AssertionError: Lists differ: [('pi[29 chars]t'), 'process_exited'] != [('pi[29 chars]t'), ('pipe_data_received', 2, b'stderr'), 'pi[57 chars]ted']