anchor.diff:  { relengapi ? { outPath = ./.; name = "relengapi-src"; }
  -, pkgs ? import (builtins.fetchTarball "https://github.com/NixOS/nixpkgs-channels/archive/954925771482b50493a24615c6e7e82e044a4fdf.tar.gz") {}
  -
  -, pythonVersion ? "python27Packages"
  +, pkgs ? import (builtins.fetchTarball "https://github.com/NixOS/nixpkgs-channels/archive/f673243aff0bc9ae4d2e96ccd60124ff9fe5b103.tar.gz") {}
   , ldap ? true
   , develop ? true
   }:
   
   let
   
  -  pythonPackages = builtins.getAttr pythonVersion pkgs;
  +  pythonPackages = pkgs.python27.pkgs;
   
     fromRequirements = requirementsFile: map
       (specification:
  
positive.code:       version = "4.0.3";
        md5 = "16d4c8e79510ba427fb5336e15b0ea34";
        deps =
          (with self; [ decorator pickleshare simplegeneric traitlets requests pexpect ]) ++
          (with pythonPackages.python.modules; [ readline sqlite3 ]);
        LC_ALL="en_US.UTF-8";
        buildInputs = with self; [ nose pkgs.glibcLocales Pygments mock ];
        patchPhase = ''
  
negative.code:   propagatedBuildInputs = 
      (fromRequirements ./requirements.txt)
      ++ pkgs.lib.optionals ldap (fromRequirements ./requirements-ldap.txt);
    doCheck = true;  # TODO: skip tests for now since they dont run in nix's restricted env
    checkPhase = ''
      export RELENGAPI_SETTINGS=settings_example.py
      export VIRTUAL_ENV=something
  