openra: use python3

pkgs/games/openra/common.nix

···
     and out-of-tree mod packages (mod.nix).
 */
 { lib, makeSetupHook, curl, unzip, dos2unix, pkg-config, makeWrapper
-, lua, mono, dotnetPackages, python2
+, lua, mono, dotnetPackages, python3
 , libGL, freetype, openal, SDL2
 , zenity
 }:
···
 with lib;
 
 let
-  path = makeBinPath ([ mono python2 ] ++ optional (zenity != null) zenity);
+  path = makeBinPath ([ mono python3 ] ++ optional (zenity != null) zenity);
   rpath = makeLibraryPath [ lua freetype openal SDL2 ];
   mkdirp = makeSetupHook { } ./mkdirp.sh;
 
···
       makeWrapper
       mkdirp
       mono
-      python2
+      python3
     ];
 
     makeFlags = [ "prefix=$(out)" ];