added on_delete in models an migrations for django 2.0

compatibility.

src/events/models.py

@@ -4,10 +4,10 @@ import os
 from ckeditor.fields import RichTextField
 from django.conf import settings
 from django.core.exceptions import ValidationError
-from django.urls import reverse
 from django.db import models
 from django.db.models import Q
 from django.template.defaultfilters import slugify
+from django.urls import reverse
 from django.utils.timezone import now
 from django.utils.translation import ugettext as _
 from easy_thumbnails.fields import ThumbnailerImageField
@@ -51,7 +51,7 @@ class Event(models.Model):
     """An Event that could be a tournament, a game session, or an convention."""
     name = models.CharField(_('Name'), max_length=255)
     description = RichTextField(_("Description"), blank=True)
-    location = models.ForeignKey('Location')
+    location = models.ForeignKey('Location', on_delete=models.PROTECT)
     start = models.DateTimeField(_('Start'))
     end = models.DateTimeField(_('End'), blank=True, null=True)
     url = models.URLField(_('Homepage'), blank=True)
@@ -220,13 +220,14 @@ class Photo(models.Model):
         upload_to=get_upload_path,
         storage=OverwriteStorage()
     )
-    event = models.ForeignKey('events.Event')
+    event = models.ForeignKey('events.Event', on_delete=models.PROTECT, )
     description = models.TextField(
         _("Description"),
         max_length=300,
         blank=True
     )
-    photographer = models.ForeignKey(settings.AUTH_USER_MODEL)
+    photographer = models.ForeignKey(settings.AUTH_USER_MODEL,
+                                     on_delete=models.PROTECT)
     on_startpage = models.BooleanField(
         _("Startpage"),
         default=False,