Require openshift_image_tag in the inventory with openshift-enterprise

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

roles/docker/tasks/main.yml

@@ -10,6 +10,14 @@
     l_use_crio: "{{ openshift_use_crio | default(False) }}"
     l_use_crio_only: "{{ openshift_use_crio_only | default(False) }}"
 
+- when:
+    - openshift_deployment_type == 'openshift-enterprise'
+  assert:
+    that:
+      - "openshift_image_tag is defined"
+    msg: >
+      openshift_image_tag is a required inventory variable when installing openshift-enterprise
+
 - name: Use Package Docker if Requested
   include: package_docker.yml
   when: