title: Don’t close Dialog on pressing OK button of QMessageBox
body: <p>I have called <em>QMessageBox()</em> like this:</p>
  
  <pre><code>class Main(QDialog):
      def __init__(self):
          self.view = QUiLoader().load("app.ui", self)
          self.view.show()
          self.functionA()
      ....
      functionA():
          try:
              ....
          except Exception:
              QMessageBox.critical(self, "Error", "System Failure")
  
  def main():
      app = QApplication(sys.argv)
      a = Main()
      sys.exit(app.exec_())
  
  if __name__ == "__main__"
      main()
  </code></pre>
  
  <p>When i click OK button of Message box it also closes my <em>Dialog</em>. How to avoid this ?</p>