fix: callback inappropriately suppresses asyncio logs

[BobTheBuidler]

This fixes something I broke in my previous PR.

What do these changes do?

We must use the private _exception attribute instead of exception() so asyncio does not set task.__log_traceback = False on the false assumption that the caller read the task Exception

Are there changes in behavior for the user?

The suppressed logs from asyncio will no longer be suppressed and behavior will work as expected in a normal asyncio application

Related issue number

N/A

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.78%. Comparing base (442ca3e) to head (8878460).
⚠️ Report is 9 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #725   +/-   ##
=======================================
  Coverage   96.78%   96.78%           
=======================================
  Files          13       13           
  Lines         809      809           
  Branches       44       44           
=======================================
  Hits          783      783           
  Misses         23       23           
  Partials        3        3           

Flag	Coverage Δ
unit	95.42% <100.00%> (ø)

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[codspeed-hq]

CodSpeed Performance Report

Merging #725 will not alter performance

_{Comparing BobTheBuidler:patch-6 (8878460) with master (442ca3e)¹}

Summary

✅ 63 untouched
⏩ 4 skipped²

Footnotes

1. No successful run was found on master (9ab48ab) during the generation of this report, so 442ca3e was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

2. 4 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[Dreamsorcerer]

Any chance of a regression test? e.g. Using caplog: https://docs.pytest.org/en/stable/how-to/logging.html#caplog-fixture