title: How to get failed hosts in fabric
body: <p>I am using fabric and have a lot of hosts I have to process.</p>
  
  <p>If any hosts fails I continue with execution with:</p>
  
  <pre><code>env.warn_only = True
  </code></pre>
  
  <p>However I want to get a list of hosts at the end that failed.  How?  I tried the below and I get nothing for either a success or fail.</p>
  
  <pre><code>error_list= []
  success_list = []
  @parallel
  def my_run():
      try:
          sudo('sh test.sh')
          success_list.append(env.host)
      except:
          error_this.append(env.host)
  
  error_list= []
  success_list = []
  </code></pre>