'Extends setPlainText to emit the new_text_set signal.
:param txt: The new text to set.
:param mime_type: Associated mimetype. Setting the mime will update the
pygments lexer.
:param encoding: text encoding'

def setPlainText(self, txt):

    super(CodeEditor, self).setPlainText(txt)
    self.new_text_set.emit()
