anchor.diff:  { lib, buildPythonPackage, pythonOlder, fetchPypi, isPy3k, isPyPy
   , atomicwrites
   , attrs
  -, funcsigs
   , hypothesis
   , iniconfig
  -, mock
   , more-itertools
   , packaging
   , pathlib2
   , pluggy
   , py
   , pygments
  -, python
   , setuptools
  -, setuptools_scm
  +, setuptools-scm
   , six
   , toml
   , wcwidth
  
positive.code: }:
  
  buildPythonPackage rec {
    version = "6.1.2";
    pname = "pytest";
  
    disabled = !isPy3k;
  
    src = fetchPypi {
      inherit pname version;
      sha256 = "c0a7e94a8cdbc5422a51ccdad8e6f1024795939cc89159a0ae7f0b316ad3823e";
    };
  
    checkInputs = [ hypothesis pygments ];
    nativeBuildInputs = [ setuptools_scm ];
    propagatedBuildInputs = [
      atomicwrites
      attrs
  
negative.code:     toml
      wcwidth
    ] ++ lib.optionals (pythonOlder "3.6") [ pathlib2 ];
  
    checkInputs = [
      hypothesis
      pygments
    ];
  
    doCheck = !isPyPy; # https://github.com/pytest-dev/pytest/issues/3460
  
  