nodejs: add python to passthru

so nodeEnv uses the exact same version.

See also https://github.com/svanderburg/node2nix/issues/25

pkgs/development/web/nodejs/nodejs.nix

@@ -67,4 +67,6 @@ in
       maintainers = with maintainers; [ goibhniu havvy gilligan cko ];
       platforms = platforms.linux ++ platforms.darwin;
     };
+
+    passthru.python = python2; # to ensure nodeEnv uses the same version
 }