anchor.diff:    nipy = buildPythonPackage rec {
       version = "0.4.0";
       name = "nipy-${version}";
  - 
  +
       disabled = pythonOlder "2.6";
   
       checkPhase = ''    # wants to be run in a different directory
  
positive.code:     };
    };
  
    pytools = buildPythonPackage rec { 
      name = "pytools-${version}"; 
      version = "2016.2.1"; 
  
      src = pkgs.fetchFromGitHub {
        owner = "inducer";
  
negative.code:         --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";
      };
    };
  }
  