anchor.diff:  
   python3Packages.buildPythonApplication rec {
     pname = "xonsh";
  -  version = "0.11.0";
  +  version = "0.13.0";
   
     # fetch from github because the pypi package ships incomplete tests
     src = fetchFromGitHub {
       owner = "xonsh";
       repo = "xonsh";
       rev = version;
  -    sha256 = "sha256-jfxQMEVABTOhx679V0iGVX9RisuY42lSdztYXMLwdcw=";
  +    sha256 = "sha256-8X/+mQrwJ0yaUHRKdoY3G0P8kq22hYfRK+7WRl/zamc=";
     };
   
     LC_ALL = "en_US.UTF-8";
  
positive.code:     "test_colorize_file"
      "test_loading_correctly"
      "test_no_command_path_completion"
      # fails on non-interactive shells
      "test_capture_always"
      "test_casting"
  
negative.code:   ];
  
    postInstall = ''
      wrapProgram $out/bin/xonsh \
        $makeWrapperArgs
    '';
  
  