Regression: 3.13 `traceback.format_list()` breaking behavior change.

Bug report

Bug description:

traceback.format_list() no longer works with lines that have breaks in them:

import traceback
import sys

print(f"Python {sys.version_info.major}.{sys.version_info.minor}")

# Frame with multiline text (source + variable annotations)
frames = [('test.py', 10, 'func', 'x = foo + bar\n\t\thello\n\tworld')]

print("\nInput (3 lines):")
print(repr(frames[0][3]))

print("\nOutput from traceback.format_list():")
result = traceback.format_list(frames)[0] # Yes, it't always a 1-element list both on 3.12 adn 3.13.
print(result)

Python 3.12

Input (3 lines):
'x = foo + bar\n\t\thello\n\tworld'

Output from traceback.format_list():
  File "test.py", line 10, in func
    x = foo + bar
                hello
        world

Python 3.13

Input (3 lines):
'x = foo + bar\n\t\thello\n\tworld'

Output from traceback.format_list():
  File "test.py", line 10, in func
    x = foo + bar

This broke bettre_exceptions on 3.13, which was fixed by formatting the traceback manually. Can we either

• Revert to old behavior in 3.15 and maybe document that it was broken in 3.13 and 3.14?
• Document the behavior change?

ref: https://github.com/Qix-/better-exceptions/issues/134

CPython versions tested on:

3.13

Operating systems tested on:

No response

Linked PRs

• gh-153469

提供されたスクリプトを Python 3.12 と 3.13 で再現し、次に traceback.format_list() から調査を始めます。互換性を意図しているのか、ドキュメント化を意図しているのかを判断する前に、リンクされた PR gh-153469 と traceback 周辺の挙動を確認してください。受け入れられた挙動が実装または文書化され、複数行のケースが関連するテストでカバーされていれば完了です。