Display the file ``fileName``.

def loadFile(self, fileName):
        """
        Display the file ``fileName``.
        """

        self.fileName = fileName
        # Assign QFile object with the current name.
        self.file = QtCore.QFile(fileName)
        if self.file.exists():
            # Load the file into the widget and reset the undo stack
            # to delete the undo object create by the setText method.
            # Without it, an undo operation would delete the content
            # of the widget which is intuitive.
            self.qteScintilla.setText(open(fileName).read())
            self.qteScintilla.qteUndoStack.reset()
        else:
            msg = "File <b>{}</b> does not exist".format(self.qteAppletID())
            self.qteLogger.info(msg)