How to Make Ansible variable mandatory : <p>I'm looking for the way how to make Ansible to analyze playbooks for required and mandatory variables before run playbook's execution like:</p>

<pre><code>- name: create remote app directory hierarchy
  file:
    path: "/opt/{{ app_name | required }}/"
    state: directory
    owner: "{{ app_user | required }}"
    group: "{{ app_user_group | required }}"
  ...
</code></pre>

<p>and rise error message if variable is undefined, like:</p>

<pre><code>please set "app_name" variable before run (file XXX/main.yml:99)
</code></pre>
