Making the example working for Django 2.1.2

Author: alqinae

examples/cookbook-plain/cookbook/ingredients/migrations/0003_auto_20181018_1746.py

@@ -0,0 +1,17 @@
+# Generated by Django 2.0 on 2018-10-18 17:46
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('ingredients', '0002_auto_20161104_0050'),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name='category',
+            options={'verbose_name_plural': 'Categories'},
+        ),
+    ]

examples/cookbook-plain/cookbook/recipes/migrations/0003_auto_20181018_1728.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.0 on 2018-10-18 17:28
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('recipes', '0002_auto_20161104_0106'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='recipeingredient',
+            name='unit',
+            field=models.CharField(choices=[('unit', 'Units'), ('kg', 'Kilograms'), ('l', 'Litres'), ('st', 'Shots')], max_length=20),
+        ),
+    ]