title: QMessageBox warning yellow exclamation mark icon
body: <p>How is possible to display a <code>QMessageBox::warning</code> with the triangular exclamation mark symbol like the one following?</p>
  
  <p><img src="https://i.stack.imgur.com/wvBY4.png" alt="Yellow background triangular exclamation mark"></p>
  
  <p>I can't find any option in <code>QMessageBox::warning</code>, I only get the red circular symbol.</p>