anchor.diff:  { python, setuptools, makeWrapper, lib }:
   
   { name, namePrefix ? "python-", src, meta, patches ? []
  -, doCheck ? true, ... } @ attrs:
  +, doCheck ? true, checkPhase ? "python setup.py test"
  +, postInstall ? ""
  +, ... } @ attrs:
   
   let
       # Return the list of recursively propagated build inputs of PKG.
  
positive.code:     echo "installing \`${name}' with \`easy_install'..."
      export PYTHONPATH="$out/lib/${python.libPrefix}/site-packages:$PYTHONPATH"
      easy_install --prefix="$out" .
    '';
  
    postFixup = ''
  
negative.code: 
    buildPhase = "true";
  
    # XXX: Should we run `easy_install --always-unzip'?  It doesn't seem
    # to have a noticeable impact on small scripts.
    installPhase = ''
  