Install php5-gd dependency for selfoss.

roles/news/tasks/selfoss.yml

 - name: Set selfoss permissions
   action: file owner=www-data group=www-data path=/var/www/selfoss recurse=yes state=directory
 
+- name: Install selfoss dependencies
+  apt: pkg={{ item }} state=present
+  with_items:
+    - php5
+    - php5-pgsql
+    - php5-gd
+
 - name: Create database user for selfoss
   postgresql_user: login_host=localhost login_user={{ db_admin_username }} login_password="{{ db_admin_password }}" name={{ selfoss_db_username }} password="{{ selfoss_db_password }}" state=present