anchor.diff:  
     python34Packages = python34.pkgs;
   
  -  python35Packages = recurseIntoAttrs python35.pkgs;
  -
  -  python36Packages = python36.pkgs;
  +  python35Packages = python35.pkgs;
  +
  +  python36Packages = recurseIntoAttrs python36.pkgs;
   
     pypyPackages = pypy.pkgs;
   
  
positive.code:   python36Full = python36.override{x11Support=true;};
  
    # pythonPackages further below, but assigned here because they need to be in sync
    pythonPackages = python2Packages;
    python2Packages = python27Packages;
    python3Packages = python35Packages;
  
    python27 = callPackage ../development/interpreters/python/cpython/2.7 {
      self = python27;
  
negative.code:   # available as `pythonPackages.tkinter` and can be used as any other Python package.
    python = python2;
    python2 = python27;
    python3 = python36;
  
    # Python interpreter that is build with all modules, including tkinter.
    # These are for compatibility and should not be used inside Nixpkgs.
  