anchor.diff:  
     buildPhase = "true";
   
  -  # Many packages, but not all, support this.
  -  checkPhase = "python setup.py test";
  -
     # XXX: Should we run `easy_install --always-unzip'?  It doesn't seem
     # to have a noticeable impact on small scripts.
     installPhase = ''
  
positive.code: { python, setuptools, makeWrapper, lib }:
  
  { name, namePrefix ? "python-", src, meta, patches ? []
  , doCheck ? true, ... } @ attrs:
  
  let
      # Return the list of recursively propagated build inputs of PKG.
  
negative.code:   //
  
    (rec {
    inherit src meta patches doCheck checkPhase;
  
    name = namePrefix + attrs.name;
  
  