anchor.diff: -{ lib
  +{ stdenv
   , buildPythonPackage
   , fetchPypi
   , pytest
  
positive.code:     pytest
    ];
  
    checkPhase = ''
      export HOME=$(mktemp -d)
      mkdir -p $HOME/.config/matplotlib
  
negative.code:     pytest
    '';
  
    meta = with stdenv.lib; {
      description = "Pytest plugin to help with testing figures output from Matplotlib";
      homepage = https://github.com/matplotlib/pytest-mpl;
      license = licenses.bsd3;
  