fix(celery): ensure error.message tag does not include stacktrace

[wconti27]

Motivation

User reported that the celery exception traceback was being included in the error.message span tag. The error was due to us using the whole exception class, which includes the traceback, to set as the error message, instead of just the exception message. Updated test to ensure just error message is returned.

Checklist

• [x] Change(s) are motivated and described in the PR description
• [x] Testing strategy is described if automated tests are not included in the PR
• [x] Risks are described (performance impact, potential for breakage, maintainability)
• [x] Change is maintainable (easy to change, telemetry, documentation)
• [x] Library release note guidelines are followed or label changelog/no-changelog is set
• [x] Documentation is included (in-code, generated user docs, public corp docs)
• [x] Backport labels are set (if applicable)
• [x] If this PR changes the public interface, I've notified @DataDog/apm-tees.

Reviewer Checklist

• [x] Title is accurate
• [x] All changes are related to the pull request's stated goal
• [x] Description motivates each change
• [x] Avoids breaking API changes
• [x] Testing strategy adequately addresses listed risks
• [x] Change is maintainable (easy to change, telemetry, documentation)
• [x] Release note makes sense to a user of the library
• [x] Author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• [x] Backport labels are set in a manner that is consistent with the release branch maintenance policy

[datadog-dd-trace-py-rkomorn[bot]]

Datadog Report

Branch report: conti/fix-celery-error-message Commit report: efbb86d Test service: dd-trace-py

:white_check_mark: 0 Failed, 237 Passed, 39 Skipped, 23m 15.65s Total duration (1.08s time saved)

[pr-commenter[bot]]

Benchmarks

Benchmark execution time: 2024-06-18 18:17:51

Comparing candidate commit ed0feff206fc101e5eeaed24e65363b75ca3e535 in PR branch conti/fix-celery-error-message with baseline commit c0bc1eb92f79a1fd5dd82a838e5923c437ee77a1 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 221 metrics, 9 unstable metrics.