Fix unit tests running against Redis 4.0.0

[AvitalFineRedis]

Pull Request check-list

Please make sure to review and check all of these items:

• Does $ tox pass with this change (including linting)?
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Description of change

closes #1698

[codecov-commenter]

Codecov Report

Merging #1699 (3908633) into master (5be96b9) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1699   +/-   ##
=======================================
  Coverage   92.21%   92.21%           
=======================================
  Files          53       53           
  Lines       11002    11006    +4     
=======================================
+ Hits        10145    10149    +4     
  Misses        857      857           

Impacted Files	Coverage Δ
tests/test_commands.py	99.80% <100.00%> (+<0.01%)	⬆️

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