Update config.yml

Author: kefo

.circleci/config.yml

@@ -18,7 +18,8 @@ jobs:
       - run:
           name: Install testing prerequisites
           command: |
-            # sudo apt-get update
+            sudo apt-get update
+            sudo apt-get install -y xsltproc
             mkdir /tmp/saxon/
             mkdir /tmp/saxon/lib/