BIG UPD: migrate to python 3.10 and django 3.2

dav_events/models/eventchange.py

@@ -3,7 +3,6 @@ from __future__ import unicode_literals
 from django.conf import settings
 from django.db import models
 from django.utils import timezone
-from django.utils.encoding import python_2_unicode_compatible
 
 from . import get_ghost_user, get_system_user
 
@@ -12,7 +11,6 @@ def get_system_user_id():
     return get_system_user().id
 
 
-@python_2_unicode_compatible
 class EventChange(models.Model):
     UPDATE = 'update'
     RAISE_FLAG = 'set_flag'
@@ -23,7 +21,7 @@ class EventChange(models.Model):
         (LOWER_FLAG, 'Lower Flag'),
     )
 
-    event = models.ForeignKey('dav_events.Event', related_name='changes')
+    event = models.ForeignKey('dav_events.Event', related_name='changes', on_delete=models.CASCADE)
     timestamp = models.DateTimeField(default=timezone.now)
     user = models.ForeignKey(settings.AUTH_USER_MODEL,
                              default=get_system_user_id,