import sys
from PySide2.QtWidgets import QWidget, QPlainTextEdit, QApplication, QVBoxLayout
from PySide2.QtCore import QMimeData


class TextEditRemoveMime1(QPlainTextEdit):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

    def createMimeDataFromSelection(self):
        mime = super().createMimeDataFromSelection()

        mime.clear()
        mime.setData("text/plain", b"")
        mime.setText(self.textCursor().selectedText())
        mime.setHtml("")

        return mime


class TextEditRemoveMime2(QPlainTextEdit):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

    def createMimeDataFromSelection(self):
        mime = QMimeData()
        text = self.textCursor().selectedText()
        mime.setText(text)
        return mime


class Example(QWidget):
    def __init__(self):
        super().__init__()
        vbox = QVBoxLayout()

        # Has styleing information
        plainTextEdit = QPlainTextEdit(self)
        vbox.addWidget(plainTextEdit)

        # Still has styleing information, does not crash
        plainTextEdit = TextEditRemoveMime1(self)
        vbox.addWidget(plainTextEdit)

        # Crashes in PySide2 but does work as expected in PyQt5
        plainTextEdit = TextEditRemoveMime2(self)
        vbox.addWidget(plainTextEdit)

        self.setLayout(vbox)
        self.show()


if __name__ == "__main__":

    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())