gh-157778: Include opening brace line in multiline f-string errors - #157779

I like the new feature (more complete error message), but I feel unable to review this change. At least, it adds tests, good!

No problem was just in case you wanted to take a look!

@pablogsal added the needs backport to 3.15 label

It might be a little bit late to change error messages in Python 3.15, no? Some projects may start relaying on Python 3.15.0 error messages.

@pablogsal added the needs backport to 3.15 label

It might be a little bit late to change error messages in Python 3.15, no? Some projects may start relaying on Python 3.15.0 error messages.

We have never promised the stability of error messages, specially syntax errors. If you feel strongly I will not backport it but otherwise I think is beneficial and we have done it before (is a fix on the error message).

I don't feel strongly, if you're confident, go ahead on the backport :-)

Thanks @pablogsal for the PR 🌮🎉.. I'm working now to backport this PR to: 3.15.
🐍🍒⛏🤖

Sorry, @pablogsal, I could not cleanly backport this to 3.15 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 1cdd590cb547597ab64b20c4b8a0c5b5b2f62b7a 3.15

GH-158047 is a backport of this pull request to the 3.15 branch.

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot x86-64 macOS 3.15 (tier-2) has failed when building commit 3b9fa19.

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/#/builders/2031/builds/377) and take a look at the build logs.
4. Check if the failure is related to this commit (3b9fa19) 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/#/builders/2031/builds/377

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

==

Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.15.billenstein-macos/build/Lib/unittest/case.py", line 637, in _callTestMethod
    result = method()
ResourceWarning: unclosed <socket.socket fd=7, family=2, type=1, proto=6, laddr=('127.0.0.1', 61375)>
k


Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.15.billenstein-macos/build/Lib/unittest/case.py", line 637, in _callTestMethod
    result = method()
ResourceWarning: unclosed <socket.socket fd=7, family=2, type=1, proto=6, laddr=('127.0.0.1', 65232)>
k