When last_version is deleted, do not delete text and previous versions in cascade, but really delete text only when there is no previous version, otherwise update text.last_version with previous version.
import logging
from django.db.models import signals
def logger_config():
# create logger
logger = logging.getLogger()
ch = logging.StreamHandler()
# create formatter
formatter = logging.Formatter("%(asctime)s - %(levelname)s - %(name)s - %(module)s - %(funcName)s - %(message)s")
# add formatter to ch
ch.setFormatter(formatter)
# add ch to logger
logger.addHandler(ch)
logger_config()