convert redirect to new python convention

build.sh

@@ -342,7 +342,7 @@ then
       done
 
       if [ $have_private_repo = true ]; then
-        $python_command  $(native_path "$helper/hg/bin/redirect.py") "${private_S3PROXY_URL}${S3PREFIX}repo/$repo/rev/$revision/index.html"\
+        python_cmd "$helpers/redirect.py" "${private_S3PROXY_URL}${S3PREFIX}repo/$repo/rev/$revision/index.html"\
             >"$build_log_dir/private.html" || fatal "generating global redirect"
         upload_output global_redirect "$build_log_dir/private.html" text/html private
       fi