UPD: small steps to become python3 compatible.

dav_events/models/eventflag.py

@@ -1,6 +1,8 @@
+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 ..utils import get_ghost_user, get_system_user
 
@@ -9,6 +11,7 @@ def get_system_user_id():
     return get_system_user().id
 
 
+@python_2_unicode_compatible
 class EventFlag(models.Model):
     event = models.ForeignKey('dav_events.Event', related_name='flags')
     status = models.ForeignKey('dav_events.EventStatus',
@@ -23,9 +26,9 @@ class EventFlag(models.Model):
     class Meta:
         ordering = ['event', 'timestamp', 'status']
 
-    def __unicode__(self):
-        s = u'{status} - {timestamp}'
+    def __str__(self):
+        s = '{status} - {timestamp}'
         if self.user:
-            s += u' by user {user}'
+            s += ' by user {user}'
         return s.format(status=self.status, timestamp=self.timestamp.strftime('%d.%m.%Y %H:%M:%S'),
                         user=self.user)