title: rsync skip non existing files on source
body: <p>I'm developing a script in python that could collect logs from multiple machines. I'm using rsync. But there's a problem. I have logs for multiple services that look like:  </p>
  
  <pre><code>service1.log
  service2.log
  service3.log
  ... and so on
  </code></pre>
  
  <p>Paths to this files and folders are specified in code. But sometimes I get in situation when some log files do not exist yet. And rsync does not finish successfully.<br>
  How can I skip files that do not exist on source machine?<br>
  P.S. I'm using saltstack to rule machines, so I call:  </p>
  
  <pre><code>__salt__['cmd.retcode']('rsync -a file1 file2...')
  </code></pre>