In Django 2.0 ForeinKeys must have on_delete

Author: Martin Pauly

test_haystack/core/models.py

@@ -17,7 +17,7 @@ class MockModel(models.Model):
     author = models.CharField(max_length=255)
     foo = models.CharField(max_length=255, blank=True)
     pub_date = models.DateTimeField(default=datetime.datetime.now)
-    tag = models.ForeignKey(MockTag)
+    tag = models.ForeignKey(MockTag, on_delete=models.CASCADE)
 
     def __unicode__(self):
         return self.author
@@ -108,4 +108,4 @@ class OneToManyLeftSideModel(models.Model):
 
 
 class OneToManyRightSideModel(models.Model):
-    left_side = models.ForeignKey(OneToManyLeftSideModel, related_name='right_side')
+    left_side = models.ForeignKey(OneToManyLeftSideModel, related_name='right_side', on_delete=models.CASCADE)