Make it more explicit that rhsm_activation_key and rhsm_repos are exclusive

If the operator is using an activation key, the repositories that are
associated to the subscription are configured in the Red Hat portal or in the
local instance of Satellite if any.
We can't specify rhsm_repos parameter if you are using rhsm_activation_key.
Otherwise, if you we rhsm_username and rhsm_password, we can use rhsm_repos
to select which parameters are deployed.

This patch:
- adds a debug message in the tasks/main when both options are defined.
- documents this situation in the README.
- adds 2 use cases in the README, one with Satellite and one with
  Portal.

Change-Id: I6448d2f7258c2b00b8617f8e12fd06b53d28dc83

README.md

@@ -59,8 +59,20 @@ Dependencies
 
 None.
 
-Example Playbook
-----------------
+
+About repositories
+------------------
+
+If you are using an activation key, the repositories that are associated to
+the subscription are configured in the Red Hat portal or in your local
+instance of Satellite. You can't specify rhsm_repos parameter if you are
+using rhsm_activation_key.
+Otherwise, if you use rhsm_username and rhsm_password, you can use rhsm_repos
+to select which parameters are deployed.
+
+
+Example Playbook with Red Hat portal
+------------------------------------
 
 ::
 
@@ -69,9 +81,26 @@ Example Playbook
         rhsm_username: bob.smith@acme.com
         rhsm_password: "{{ vault_rhsm_password }}"
         rhsm_repos:
+          - rhel-7-server-rpms
           - rhel-7-server-extras-rpms
           - rhel-7-server-rh-common-rpms
-          - rhel-7-server-openstack-8-rpms
+          - rhel-ha-for-rhel-7-server-rpms
+      roles:
+        - openstack.redhat-subscription
+
+Example Playbook with Satellite 6
+---------------------------------
+
+::
+
+    - hosts: all
+      vars:
+        rhsm_activation_key: "secrete_key"
+        rhsm_org_id: "Default_Organization"
+        rhsm_server_hostname: "mysatserver.com"
+        rhsm_baseurl: "https://mysatserver.com/pulp/repos"
+        rhsm_method: satellite
+        rhsm_insecure: yes
       roles:
         - openstack.redhat-subscription
 

tasks/main.yml

@@ -4,6 +4,13 @@
   tags:
     - rhsm
 
+- name: Inform the operators if both rhsm_activation_key and rhsm_repos are given
+  debug:
+    msg: "rhsm_repos and rhsm_activation_key are exclusive options"
+  when:
+    - rhsm_repos | length > 0
+    - rhsm_activation_key is defined
+
 - name: Configure Red Hat Subscription Manager
   template:
     src: rhsm.conf.j2