add missing imports

src/tickets/models.py

@@ -17,10 +17,6 @@ from utils.models import (
 from utils.pdf import generate_pdf_letter
 from django.db import models
 from django.db.models.signals import post_save
-from datetime import (
-    timedelta,
-    datetime
-)
 from django.db.models import Count
 from ircbot.models import OutgoingIrcMessage
 

src/tickets/signals.py

@@ -1,4 +1,8 @@
 from django.conf import settings
+from datetime import (
+    timedelta,
+    datetime
+)
 
 def ticket_changed(sender, instance, created, **kwargs):
     """