title: Ansible prompt and check_mode
body: <p>I have a "vars_prompt" setup for the "check_mode" option:</p>
  
  <pre><code>---
   - name: Test check_mode from prompt
     hosts: localhost
  
     vars_prompt:
     - name: "check_mode"
       prompt: "Check mode: yes(default)=check-only, no=execute commands"
       private: no
       default: true
  
     tasks:
     - name: msg="False test | {{ check_mode }}"
       debug: var=check_mode
       when: not check_mode
  
     - name: msg="True test | {{ check_mode }}"
       debug: var=check_mode
       when: check_mode
  </code></pre>
  
  <p>When I run the playbook (<code>ansible-playbook -i myhosts test.yml</code>) and answer <code>true</code> or <code>false</code> the tests work as expected, but when I use "yes" and "no" (as the <a href="http://docs.ansible.com/ansible/playbooks_checkmode.html" rel="nofollow">http://docs.ansible.com/ansible/playbooks_checkmode.html</a> document mentions), I get this error:</p>
  
  <pre><code>The conditional check 'check_mode' failed. The error  was: error
  while evaluating conditional (check_mode): 'no' is undefined
  </code></pre>
  
  <p>Is this an error in the document, or in how I'm using the <code>check_mode</code> variable in the <code>when</code> clause?  It was my impression that true/yes and false/no were automagically handled.</p>