[PR #5776/9c084aea backport][3.8] Show all Sphinx warnings together

[patchback]

This is a backport of PR #5776 as merged into master (9c084ae).

What do these changes do?

This change makes sure that all the warnings are shown during sphinx-build runs.

Are there changes in behavior for the user?

Nope.

Related issue number

#5518

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modification, please add yourself to CONTRIBUTORS.txt
  • The format is <Name> <Surname>.
  • Please keep alphabetical order, the file is sorted by names.
• Add a new news fragment into the CHANGES folder
  • name it <issue_id>.<type> for example (588.bugfix)
  • if you don't have an issue_id change it to the pr id after creating the pr
  • ensure type is one of the following:
    • .feature: Signifying a new feature.
    • .bugfix: Signifying a bug fix.
    • .doc: Signifying a documentation improvement.
    • .removal: Signifying a deprecation or removal of public API.
    • .misc: A ticket has been closed, but it is not of interest to users.
  • Make sure to use full sentences with correct case and punctuation, for example: "Fix issue with non-ascii contents in doctest text files."

[codecov]

Codecov Report

Merging #5777 (9c084ae) into 3.8 (8ce3013) will decrease coverage by 2.57%.
The diff coverage is 95.56%.

❗ Current head 9c084ae differs from pull request most recent head 77b2944. Consider uploading reports for the commit 77b2944 to get more accurate results

@@            Coverage Diff             @@
##              3.8    #5777      +/-   ##
==========================================
- Coverage   97.53%   94.96%   -2.58%     
==========================================
  Files          44       41       -3     
  Lines        8844     8832      -12     
  Branches     1424     1416       -8     
==========================================
- Hits         8626     8387     -239     
- Misses        102      317     +215     
- Partials      116      128      +12     

Flag	Coverage Δ
unit	94.96% <95.56%> (-2.42%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
aiohttp/web_protocol.py	85.50% <ø> (-5.11%)	⬇️
aiohttp/web_request.py	95.98% <ø> (-1.58%)	⬇️
aiohttp/web_response.py	97.99% <ø> (-0.29%)	⬇️
aiohttp/web_routedef.py	98.13% <ø> (+0.03%)	⬆️
aiohttp/web_runner.py	92.34% <ø> (-5.29%)	⬇️
aiohttp/web_server.py	94.28% <ø> (-5.72%)	⬇️
aiohttp/web_urldispatcher.py	97.54% <ø> (-0.06%)	⬇️
aiohttp/worker.py	6.77% <ø> (-89.95%)	⬇️
aiohttp/resolver.py	60.00% <62.50%> (-35.17%)	⬇️
aiohttp/locks.py	92.85% <66.66%> (ø)
... and 69 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e84e4d4...77b2944. Read the comment docs.