Print stacktrace when catching TimeoutError

[bitrut]

What do these changes do?

When TimeoutError is caught in the handler, the exception stack trace is logged.

Are there changes in behavior for the user?

Related issue number

No related issue.

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
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[codecov-io]

Codecov Report

Merging #3414 into master will decrease coverage by 0.11%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3414      +/-   ##
==========================================
- Coverage   98.01%   97.89%   -0.12%     
==========================================
  Files          44       44              
  Lines        8511     8511              
  Branches     1382     1382              
==========================================
- Hits         8342     8332      -10     
- Misses         70       76       +6     
- Partials       99      103       +4

Impacted Files	Coverage Δ
aiohttp/web_protocol.py	92.2% <100%> (ø)	⬆️
aiohttp/tcp_helpers.py	90% <0%> (-6.67%)	⬇️
aiohttp/web_fileresponse.py	96.51% <0%> (-1.75%)	⬇️
aiohttp/client_reqrep.py	96.96% <0%> (-0.49%)	⬇️
aiohttp/connector.py	97.25% <0%> (-0.35%)	⬇️

---

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[asvetlov]

Timeout is a pretty common situation.
Logging a stack trace every time can be annoying.
Maybe keeping a trace in debug mode only makes sense?

Also a test is required, at least to never miss the functionality on future refactorings.

[bitrut]

@asvetlov
My fix is the result of very long investigation of occasional tests failures in my project, which happened only on CI.
Step by step I got the point that I have set too short timeouts for the db connection.
But seeing the handler responding with http 504 without any context wasn't too helpful.

I'll try to follow your hints.

[bitrut]

@asvetlov
I added suggested changes.

[asvetlov]

Thanks!

[lock]

This thread has been automatically locked since there has not been
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related bugs.

If you feel like there's important points made in this discussion,
please include those exceprts into that new issue.