pyqt5程序卡死，且出现 assertion 'GTK_IS_WIDGET (widget)' failed等错误

Question

import sys
from PyQt5.QtWidgets import QMainWindow, QTextEdit, QAction, QApplication
from PyQt5.QtGui import QIcon


class Example(QMainWindow):
    
    def __init__(self):
        super().__init__()
        
        self.initUI()
        
        
    def initUI(self):               
        
        textEdit = QTextEdit()
        self.setCentralWidget(textEdit)

        exitAction = QAction(QIcon('exit24.png'), 'Exit', self)
        exitAction.setShortcut('Ctrl+Q')
        exitAction.setStatusTip('Exit application')
        exitAction.triggered.connect(self.close)

        self.statusBar()

        menubar = self.menuBar()
        fileMenu = menubar.addMenu('&File')
        fileMenu.addAction(exitAction)

        toolbar = self.addToolBar('Exit')
        toolbar.addAction(exitAction)
        
        self.setGeometry(300, 300, 350, 250)
        self.setWindowTitle('Main window')    
        self.show()
        
        
if __name__ == '__main__':
    
    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())
    
    

代码是按照 http://zetcode.com/gui/pyqt5/menustoolbars/ 这里的教程写的

环境：Ubuntu14.04，Python3.4，PyQt5.5

运行时报错：

(python3:3595): Gtk-CRITICAL **: IA__gtk_widget_style_get: assertion 'GTK_IS_WIDGET (widget)' failed

QWidget::setMinimumSize: (/Example) The largest allowed size is (16777215,16777215)

QXcbShmImage: shmget() failed (22) for size 1073610756 (16383x16383)