anchor.diff:  { stdenv, buildPythonPackage, fetchPypi
  -, pytest_3, setuptools_scm }:
  +, pytest, setuptools_scm }:
   
   buildPythonPackage rec {
     pname = "apipkg";
  
positive.code: 
    meta = with stdenv.lib; {
      description = "Namespace control and lazy-import mechanism";
      homepage = https://bitbucket.org/hpk42/apipkg;
      license = licenses.mit;
    };
  }
  
negative.code:   };
  
    nativeBuildInputs = [ setuptools_scm ];
    checkInputs = [ pytest ];
  
    # Fix pytest 4 support. See: https://github.com/pytest-dev/apipkg/issues/14
    postPatch = ''
      substituteInPlace "test_apipkg.py" \
        --replace "py.test.ensuretemp('test_apipkg')" "py.path.local('test_apipkg')"
    '';
  
    checkPhase = ''
      py.test
  