pyupgrade the code

[pawelrubin]

Changes

Codebase upgrade via pyupgrade --py36-plus.

Since the aiokafka package is not compatible with Python versions lower than 3.6, the codebase can be upgraded.

Checklist

I believe non of the following is applicable.

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• Add a new news fragment into the CHANGES folder
  • name it <issue_id>.<type> (e.g. 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 #752 (642fcb1) into master (158873d) will decrease coverage by 0.00%.
The diff coverage is 89.28%.

@@            Coverage Diff             @@
##           master     #752      +/-   ##
==========================================
- Coverage   97.96%   97.96%   -0.01%     
==========================================
  Files          31       31              
  Lines        5268     5266       -2     
==========================================
- Hits         5161     5159       -2     
  Misses        107      107              

Flag	Coverage Δ
cext	87.78% <89.28%> (-0.05%)	⬇️
integration	97.93% <89.28%> (-0.01%)	⬇️
purepy	97.49% <89.28%> (-0.01%)	⬇️
unit	51.51% <42.85%> (-0.04%)	⬇️

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

Impacted Files	Coverage Δ
aiokafka/producer/transaction_manager.py	98.32% <ø> (ø)
aiokafka/protocol/fetch.py	100.00% <ø> (ø)
aiokafka/protocol/produce.py	94.82% <ø> (-0.09%)	⬇️
aiokafka/protocol/transaction.py	100.00% <ø> (ø)
aiokafka/record/default_records.py	95.85% <0.00%> (ø)
aiokafka/record/legacy_records.py	98.92% <ø> (ø)
aiokafka/consumer/consumer.py	97.91% <66.66%> (ø)
aiokafka/conn.py	94.11% <85.71%> (+0.01%)	⬆️
aiokafka/client.py	98.15% <100.00%> (ø)
aiokafka/consumer/fetcher.py	97.18% <100.00%> (ø)
... and 5 more

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