Update sanity checks

tasks/main.yml

@@ -4,6 +4,7 @@
     that:
       - monitored_dont|default(False) != True
       - monitored_by_nrpe == True or monitored_by_ssh == True
+    fail_msg: "Neither monitored_by_nrpe nor monitored_by_ssh set to True"
 
 - name: Gather OS Specific Variables
   include_vars: "{{ item }}"

tasks/ssh.yml

@@ -1,4 +1,10 @@
 ---
+- name: Sanity check
+  assert:
+    that:
+      - monitored_ssh_key_files|length > 0
+    fail_msg: "List of SSH keys ('monitored_ssh_key_files') is empty!"
+
 - name: Copy SSH authorized_keys for monitoring user
   authorized_key:
     user: "{{ monitored_user }}"