title: How do I tell boto operation was successful?
body: <p>I'm doing fairy straightforward uploading with boto </p>
  
  <pre><code>for path, dirs, files in os.walk("data"):
      for file in files:
          k = Key(bucket)
          k.key = file
          k.set_contents_from_filename(os.path.join(path,file))
  </code></pre>
  
  <p>but set_contents_from_filename does not return anything. How do I tell the operation was success and not failed silently? I'm using RiakCS as a backend if it is important.</p>