Fix (#4850): Timeouts checked once a second.

[luckydenis]

What do these changes do?

Bug fix.

Replaced the ceil method with the round method with rounding to 3 decimal places. This will allow to get a timeout of less than a second.

Are there changes in behavior for the user?

Yes. Now the user can set a timeout of less than a second.

Related issue number

#4850

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
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  • if you don't have an issue_id change it to the pr id after creating the pr
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    • .feature: Signifying a new feature.
    • .bugfix: Signifying a bug fix.
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    • .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-commenter]

Codecov Report

Merging #4851 into master will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #4851   +/-   ##
=======================================
  Coverage   97.60%   97.60%           
=======================================
  Files          43       43           
  Lines        8932     8932           
  Branches     1406     1406           
=======================================
  Hits         8718     8718           
  Misses         95       95           
  Partials      119      119           

Impacted Files	Coverage Δ
aiohttp/helpers.py	96.61% <100.00%> (ø)

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[luckydenis]

@asvetlov, @webknjaz, Good evening. Apparently, tests were broken in the project (Py38-Cython-Mac, Py38-Cython-Win), according to other queries. I can't reproduce this error on Mac OS.

[asvetlov]

Superseded by #5091