title: QObject.inherits(className) works strange in PyQt5
body: <p><code>QObject.inherits(className)</code> does work different in <code>PyQt5</code> than in <code>PyQt4</code> and <code>PySide</code>.</p>
  
  <pre><code>from PyQt5 import QtWidgets
  #from PySide import QtGui
  #from PyQt4 import QtGui
  
  QtWidgets = QtGui
  
  class MyWidget(QtWidgets.QWidget):
      pass
  
  app = QtWidgets.QApplication([])
  w = MyWidget()
  print(w.inherits("MyWidget"))
  </code></pre>
  
  <p>In <code>PyQt5</code> it prints <code>False</code>, while in <code>PyQt4</code> and <code>PySide</code> (uncomment the second or third line and comment the first one) it prints <code>True</code>. Why is that and how to fix it?</p>