Avoid creating TimerContext when there is no timeout

[jcugat]

This will allow to use aiohttp with ioloops that don't implement
asyncio.Task.current_task, like Tornado's couroutine runner.

More info: #1180

What do these changes do?

This will allow to use aiohttp with ioloops that don't implement asyncio.Task.current_task, like Tornado's couroutine runner.

Are there changes in behavior for the user?

This will restore previous functionality that was available in v1.3.3, which was possible to run with Tornado when setting timeout=None. This was lost in this refactor: 38360f9

Related issue number

More information is available in the original issue: #1180

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 entry to CHANGES.rst
  • Choose any open position to avoid merge conflicts with other PRs.
  • Add a link to the issue you are fixing (if any) using #issue_number format at the end of changelog message. Use Pull Request number if there are no issues for PR or PR covers the issue only partially.

[codecov-io]

Codecov Report

Merging #1817 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1817      +/-   ##
==========================================
+ Coverage   97.18%   97.18%   +<.01%     
==========================================
  Files          37       37              
  Lines        7467     7469       +2     
  Branches     1297     1298       +1     
==========================================
+ Hits         7257     7259       +2     
  Misses         89       89              
  Partials      121      121

Impacted Files	Coverage Δ
aiohttp/helpers.py	97.59% <100%> (+0.01%)	⬆️

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[asvetlov]

I believe Tornado should fix its issue with asyncio compatibility instead of trying to invent workarounds with tornado in every async library.

[jcugat]

Yes, I agree than the best outcome would be to implement asyncio.Task.current_task in Tornado, but since this behaviour was previously possible (in aiohttp v1.3.3) but it's broken now, I'd treat this as an actual bug.

[fafhrd91]

thanks

[fafhrd91]

I am implementing alternative event loop at the moment, and asyncio.Task.current_task api is so bad and ugly.

[lock]

This thread has been automatically locked since there has not been
any recent activity after it was closed. Please open a new issue for
related bugs.

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