[mailman] Install sassc in order to compile css files

Signed-off-by: Yohann D'ANELLO <ynerant@crans.org>

roles/mailman3/tasks/main.yml

@@ -5,12 +5,13 @@
   apt:
     update_cache: true
     name:
+      - dbconfig-no-thanks  # Do not autoconfigure database
       - mailman3-full
       - nginx
-      - dbconfig-no-thanks  # Do not autoconfigure database
       - postgresql
       - python3-pip  # CAS
       - python3-lxml  # CAS
+      - sassc
     install_recommends: false
   register: apt_result
   retries: 3