[3.11] gh-93883: elide traceback indicators when possible (GH-93994)

[miss-islington]

• 3.11 backtrace visual indicators are too verbose #93883: elide traceback indicators when possible

Elide traceback column indicators when the entire line of the
frame is implicated. This reduces traceback length and draws
even more attention to the remaining (very relevant) indicators.

Example:

Traceback (most recent call last):
  File "query.py", line 99, in <module>
    bar()
  File "query.py", line 66, in bar
    foo()
  File "query.py", line 37, in foo
    magic_arithmetic('foo')
  File "query.py", line 18, in magic_arithmetic
    return add_counts(x) / 25
           ^^^^^^^^^^^^^
  File "query.py", line 24, in add_counts
    return 25 + query_user(user1) + query_user(user2)
                ^^^^^^^^^^^^^^^^^
  File "query.py", line 32, in query_user
    return 1 + query_count(db, response['a']['b']['c']['user'], retry=True)
                               ~~~~~~~~~~~~~~~~~~^^^^^
TypeError: 'NoneType' object is not subscriptable

Rather than going out of our way to provide indicator coverage
in every traceback test suite, the indicator test suite should
be responible for sufficient coverage (e.g. by adding a basic
exception group test to ensure that margin strings are covered).
(cherry picked from commit da71751)

Co-authored-by: John Belmonte [email protected]

[miss-islington]

Status check is done, and it's a success ✅ .

[miss-islington]

@belm0 and @pablogsal: Status check is done, and it's a success ❌ .

[pablogsal]

@belm0 Seems this is going to need a manual backport

[pablogsal]

Do you mind creating it using cherry_picker and tagging me in the PR?

[DanielNoord]

@belm0 and @pablogsal: Status check is done, and it's a success ❌ .

Opened python/miss-islington#564 to report miss-islington's ambivalence in this comment.

[belm0]

Do you mind creating it using cherry_picker and tagging me in the PR?

Will do, but I'm not sure what to make of this comment on the original PR-- fixing main branch CI is higher priority?

This change broke all main branch CI and buildbots. See https://github.com/python/cpython/runs/7277260781?check_suite_focus=true

#93994 (comment)

[belm0]

I think the same tests failed on this backport PR and in master (probably due to new test code that automatic merge missed). I'll fix master first, then backport.

(I've got an appointment now, but will pick this up in about 2 hrs.)