anchor.diff:        --replace 'PyPlatec==1.4.0' 'PyPlatec' \
     '';
   
  -  doCheck = true;
  -
  -  postCheck = ''
  +  # with python<3.5, unittest fails to discover tests because of their filenames
  +  # so nose is used instead.
  +  checkInputs = stdenv.lib.optional (pythonOlder "3.5") [ nose ];
  +  postCheck = stdenv.lib.optionalString (pythonOlder "3.5") ''
       nosetests tests
     '';
   
  
positive.code:     ln -s ${src-data} worldengine-data
    '';
  
    buildInputs = [ nose ];
    propagatedBuildInputs = [ noise numpy pyplatec protobuf purepng h5py gdal ];
  
    prePatch = ''
  
negative.code: { stdenv
  , buildPythonPackage
  , pythonOlder
  , fetchFromGitHub
  , nose
  , noise
  