title: get buttons with xpath with strange attribute
body: <p>in a web page I have to select all the buttons like this :</p>
  <pre><code>&lt;button :class=&quot;{'complete': isComplete, 'open': open}&quot; :disabled=&quot;orderedEvents.length === 0&quot;&gt;&lt;/button&gt;
  </code></pre>
  <p>but with this xpath :</p>
  <pre><code>//button[contains(@class, 'isComplete, \'open\'')]
  </code></pre>
  <p>do not works!</p>