Update pytest and noxfile.py

[drhagen]

Update pytest version and actually use Nox Poetry.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.15%. Comparing base (c16c59a) to head (44320f2).

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Additional details and impacted files

@@           Coverage Diff           @@
##           master      #61   +/-   ##
=======================================
  Coverage   89.15%   89.15%           
=======================================
  Files          54       54           
  Lines        2978     2978           
  Branches      534      534           
=======================================
  Hits         2655     2655           
  Misses        247      247           
  Partials       76       76           

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