gh-151540: Use a selector event loop in the happy-eyeballs tests

[jmrossi98]

test_create_connection_happy_eyeballs and test_create_connection_happy_eyeballs_ipv4_only in test.test_asyncio.test_base_events create their event loop with asyncio.new_event_loop(), which defaults to ProactorEventLoop on Windows. Creating the socket transport on that loop immediately registers the socket with a real I/O completion port via _overlapped.CreateIoCompletionPort(obj.fileno(), ...). The tests use a MagicMock socket (from test_utils.mock_nonblocking_socket()), so fileno() returns a MagicMock and the callback fails with TypeError: an integer is required. The proactor path never consults the _add_reader/_add_writer mocks the tests set up.

These tests exercise the platform-independent happy-eyeballs address selection in BaseEventLoop.create_connection(), not proactor behavior, so create the loop with asyncio.SelectorEventLoop() explicitly. This matches the code path the tests already exercise on non-Windows platforms, and follows the existing pattern in this file (BaseEventLoopWithSelectorTests) and elsewhere in test_asyncio.

Verified on Windows 11 against main: reproduced the TypeError before the change; after it, test_asyncio.test_base_events (118 tests) and the full test_asyncio suite (2547 tests) pass with no exceptions logged.

• Issue: test.test_asyncio.test_base_events failing on windows due to non-integer fileno() return #151540

[python-cla-bot]

All commit authors signed the Contributor License Agreement.

[kumaraditya303]

Test changes do not need news.

[bedevere-app]

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

[jmrossi98]

@kumaraditya303 Thank you for the update, I removed the news entry

[miss-islington-app]

Thanks @jmrossi98 for the PR, and @kumaraditya303 for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

[miss-islington-app]

Thanks @jmrossi98 for the PR, and @kumaraditya303 for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

[miss-islington-app]

Thanks @jmrossi98 for the PR, and @kumaraditya303 for merging it 🌮🎉.. I'm working now to backport this PR to: 3.15.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

[miss-islington-app]

Sorry, @jmrossi98 and @kumaraditya303, I could not cleanly backport this to 3.14 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker a1ef41ab4198db28f63fda646200b14badb96513 3.14

[miss-islington-app]

Sorry, @jmrossi98 and @kumaraditya303, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker a1ef41ab4198db28f63fda646200b14badb96513 3.13

[bedevere-app]

GH-154623 is a backport of this pull request to the 3.15 branch.

[hugovk]

@jmrossi98 Would you like to have a go at the backports?

[jmrossi98]

@hugovk Took a look and seems like test_create_connection_happy_eyeballs/_ipv4_only were added by gh-98388 (#136368) after 3.14 branched off, so they don't exist on 3.14 or 3.13. I think the bot's conflicts are just missing code, not real conflicts. Is it worth dropping the backport labels?

[hugovk]

That sounds reasonable, removed. Thanks for checking :)