nix-shell not working

gistfile1.txt

let
pkgs = import <nixpkgs> {};
fhs = pkgs.buildFHSUserEnv {
  name = "versionkeeper";
  targetPkgs = pkgs: with pkgs; [
  	     alsaLib atk cairo cups dbus expat
	     file fontconfig freetype gdb git
	     glib  gtk3-x11 gtk2-x11  libnotify libxml2
	     libxslt netcat nspr nss 
	     strace udev watch wget which xorg.libX11
    xorg.libXScrnSaver xorg.libXcomposite
    xorg.libXcursor xorg.libXdamage
    xorg.libXext xorg.libXfixes xorg.libXi
    xorg.libXrandr xorg.libXrender
    xorg.libXtst xorg.libxcb xorg.xcbutilkeysyms
    zlib zsh
    jetbrains.ruby-mine
    jetbrains.jdk
    jetbrains.webstorm
    jetbrains.datagrip
    ruby_2_4.devEnv
    freetds
    nodejs-10_x
    unzip
    openssh
    zip xml2
    procps
    
  ];
  runScript = "bash";
};
in pkgs.stdenv.mkDerivation {
   name = "versionkeeper-env-shell";
   nativeBuildInputs = [fhs];
#   shellHook = "exec versionkeeper-env";

}