anchor.diff:  
       system.activationScripts.checks.text = ''
         ${darwinChanges}
  +      ${runLink}
         ${buildUsers}
         ${nixChannels}
         ${nixInstaller}
  
positive.code:       "")
          ;;
        *)
          echo "[1;31merror: The ~/.nix-defexpr/channels symlink does not point your users channels[0m" >&2
          echo "Running nix-channel will regenerate it" >&2
          echo >&2
          echo "    rm ~/.nix-defexpr/channels" >&2
  
negative.code:       echo >&2
        echo "$darwinChanges" >&2
        echo >&2
      fi
    '';
  
    runLink = ''
      if ! test -e /run; then
          echo "[1;31merror: Directory /run does not exist, aborting activation[0m" >&2
          echo "Create a symlink to /var/run with:" >&2
          echo >&2
          echo "    sudo ln -s private/var/run /run" >&2
          echo >&2
          exit 2
      fi
    '';
  
  