ETag fixes PR #5298

[greshilov]

What do these changes do?

Small fixes for PR #5298.

Are there changes in behavior for the user?

No.

Related issue number

#5298

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 #5561 (6756810) into master (1a4126a) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #5561   +/-   ##
=======================================
  Coverage   97.21%   97.21%           
=======================================
  Files          41       41           
  Lines        8863     8863           
  Branches     1425     1425           
=======================================
  Hits         8616     8616           
  Misses        130      130           
  Partials      117      117           

Flag	Coverage Δ
unit	97.10% <100.00%> (ø)

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

Impacted Files	Coverage Δ
aiohttp/web_fileresponse.py	98.62% <100.00%> (ø)

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