Fix migration.

biscuit/apps/exlibris/migrations/0008_default_school.py

@@ -8,7 +8,7 @@ import django.db.models.deletion
 class Migration(migrations.Migration):
 
     dependencies = [
-        ('exlibris', '0006_school_book'),
+        ('exlibris', '0007_book_unique_school'),
     ]
 
     operations = [