set creditor and debtor to null=False

src/economy/migrations/0010_auto_20190330_1045.py

@@ -0,0 +1,24 @@
+# Generated by Django 2.1.7 on 2019-03-30 09:45
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('economy', '0009_auto_20190328_0715'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='expense',
+            name='creditor',
+            field=models.ForeignKey(help_text='The Creditor to which this expense belongs', on_delete=django.db.models.deletion.PROTECT, related_name='expenses', to='economy.Credebtor'),
+        ),
+        migrations.AlterField(
+            model_name='revenue',
+            name='debtor',
+            field=models.ForeignKey(help_text='The Debtor to which this revenue belongs', on_delete=django.db.models.deletion.PROTECT, related_name='revenues', to='economy.Credebtor'),
+        ),
+    ]

src/economy/models.py

@@ -149,7 +149,6 @@ class Revenue(CampRelatedModel, UUIDModel):
         'economy.Credebtor',
         on_delete=models.PROTECT,
         related_name='revenues',
-        null=True,
         help_text='The Debtor to which this revenue belongs',
     )
 
@@ -273,7 +272,6 @@ class Expense(CampRelatedModel, UUIDModel):
         'economy.Credebtor',
         on_delete=models.PROTECT,
         related_name='expenses',
-        null=True,
         help_text='The Creditor to which this expense belongs',
     )