anchor.diff:  , fetchPypi
   , hypothesis
   , pytestcache
  -, pytestflakes
  -, pytestpep8
   , pytest
   , glibcLocales
   , mock ? null
  
positive.code:   # testing based on project's tox.ini
    checkPhase = ''
      pytest --doctest-modules natsort
      pytest --flakes --pep8
    '';
  
    meta = {
  
negative.code:   checkInputs = [
      hypothesis
      pytestcache
      pytest
      glibcLocales
    ]
  