anchor.diff:  
     LC_ALL = "en_US.UTF-8";
   
  +  nativeBuildInputs = [ installShellFiles ];
  +
     postPatch = ''
       # pipenv invokes python in a subprocess to create a virtualenv
       # and to call setup.py.
  
positive.code: { lib
  , python3
  }:
  
  with python3.pkgs;
  
negative.code:   propagatedBuildInputs = runtimeDeps python3.pkgs;
  
    postInstall = ''
      installShellCompletion --cmd pipenv \
        --bash <(_PIPENV_COMPLETE=bash_source $out/bin/pipenv) \
        --zsh <(_PIPENV_COMPLETE=zsh_source $out/bin/pipenv) \
        --fish <(_PIPENV_COMPLETE=fish_source $out/bin/pipenv)
    '';
  
    doCheck = true;
  