anchor.diff:    # available as `pythonPackages.tkinter` and can be used as any other Python package.
     python = python2;
     python2 = python27;
  -  python3 = python35;
  +  python3 = python36;
   
     # Python interpreter that is build with all modules, including tkinter.
     # These are for compatibility and should not be used inside Nixpkgs.
  
positive.code:     self = python33;
      inherit (darwin) CF configd;
    };
    python34 = hiPrio (callPackage ../development/interpreters/python/cpython/3.4 {
      inherit (darwin) CF configd;
      self = python34;
    });
    python35 = hiPrio (callPackage ../development/interpreters/python/cpython/3.5 {
      inherit (darwin) CF configd;
      self = python35;
    });
    python36 = callPackage ../development/interpreters/python/cpython/3.6 {
      inherit (darwin) CF configd;
      self = python36;
  
negative.code:   python36Full = python36.override{x11Support=true;};
  
    # pythonPackages further below, but assigned here because they need to be in sync
    pythonPackages = python.pkgs;
    python2Packages = python2.pkgs;
    python3Packages = python3.pkgs;
  
    python27 = callPackage ../development/interpreters/python/cpython/2.7 {
      self = python27;
  