title: Catch an error from command line Python
body: <p>I need to catch an error from command line without print error message on the screen. When this occurs I need to give another command to run.</p>
  
  <p>This is what I do now:</p>
  
  <pre><code>hyst_cmd = "si viewhistory ..."
  process = subprocess.Popen(hyst_cmd, stdout=subprocess.PIPE)
  hyst = process.stdout.read().splitlines()
  </code></pre>
  
  <p>When I do this for some projects I receive an error message, on the screen.</p>
  
  <p>Sorry for my english!</p>