packageOverrides

{
  packageOverrides = pkgs: rec {
    ansible = pkgs.stdenv.lib.overrideDerivation pkgs.ansible (attrs: {
      version = "1.8.4";
      name = "ansible-1.8.4";
      src = pkgs.fetchurl {
        url = "http://releases.ansible.com/ansible/ansible-1.8.4.tar.gz";
        sha256 = "1hcy4f6l9c23aa05yi4mr0zbqp0c6v5zq4c3dim076yfmfrh8z6k";
      };
    });

    grin = pkgs.pythonPackages.buildPythonPackage rec {
      name = "grin-1.2.1";
      namePrefix = "";

      src = pkgs.fetchurl {
        url = "https://pypi.python.org/packages/source/g/grin/${name}.tar.gz";
        sha256 = "1swzwb17wibam8jszdv98h557hlx44pg6psv6rjz7i33qlxk0fdz";
      };

      buildInputs = with pkgs.pythonPackages; [ nose ];
      propagatedBuildInputs = with pkgs.pythonPackages; [ argparse ];

      meta = {
        homepage = https://pypi.python.org/pypi/grin;
        description = "A grep program configured the way I like it.";
        platform = pkgs.stdenv.lib.platforms.all;
        maintainers = [ "Simon Jagoe <simon@simonjagoe.com>" ];
      };
    };
  };
}