anchor.diff:          --prefix PYTHONPATH : "$PYTHONPATH"
       '';
     };
  +
  +  yapf = buildPythonPackage rec {
  +    name = "yapf-${version}";
  +    version = "0.11.0";
  +
  +    meta = {
  +      description = "A formatter for Python code.";
  +      homepage    = "https://github.com/google/yapf";
  +      license     = licenses.asl20;
  +      maintainers = with maintainers; [ siddharthist ];
  +    };
  +
  +    src = pkgs.fetchurl {
  +      url = "mirror://pypi/y/yapf/${name}.tar.gz";
  +      sha256 = "14kb9gxw39zhvrijhp066b4bm6bgv35iw56c394y4dyczpha0dij";
  +    };
  +  };
   }
  
positive.code:   nipy = buildPythonPackage rec {
      version = "0.4.0";
      name = "nipy-${version}";
   
      disabled = pythonOlder "2.6";
  
      checkPhase = ''    # wants to be run in a different directory
  
negative.code:     ];
  
      meta = {
        homepage = https://github.com/inducer/pytools/;
        description = "Miscellaneous Python lifesavers.";
        license = licenses.mit;
        maintainers = with maintainers; [ artuuge ];
  