python-openid: remove, only keep python3-openid

see discussion on
https://github.com/NixOS/nixpkgs/commit/2e41891e6d595b9acf484d7d349b17a7b35b6923

pkgs/development/python-modules/python3-openid/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, buildPythonPackage, fetchPypi, defusedxml }:
+{ stdenv, isPy3k, buildPythonPackage, fetchPypi, defusedxml }:
 
 buildPythonPackage rec {
   pname = "python3-openid";
@@ -13,6 +13,8 @@ buildPythonPackage rec {
 
   doCheck = false;
 
+  disabled = !isPy3k;
+
   meta = with stdenv.lib; {
     description = "OpenID support for modern servers and consumers";
     homepage = http://github.com/necaris/python3-openid;