version bumps and migration to django 2.2

facts/migrations/0001_initial.py

@@ -26,6 +26,6 @@ class Migration(migrations.Migration):
         migrations.AddField(
             model_name='fact',
             name='category',
-            field=models.ForeignKey(to='facts.FactCategory'),
+            field=models.ForeignKey(to='facts.FactCategory', on_delete=models.CASCADE),
         ),
     ]

facts/models.py

@@ -52,7 +52,7 @@ class Fact(models.Model):
     """Define facts."""
 
     fact = models.TextField()
-    category = models.ForeignKey(FactCategory)
+    category = models.ForeignKey(FactCategory, on_delete=models.CASCADE)
     nickmask = models.CharField(max_length=200, default='', blank=True)
     time = models.DateTimeField(auto_now_add=True)