all: fix error message on trying to delete protected models (references #3211)

netbox/ipam/tests/test_api.py

@@ -1,3 +1,5 @@
+import json
+
 from django.urls import reverse
 from netaddr import IPNetwork
 from rest_framework import status
@@ -870,6 +872,8 @@ class VLANTest(APITestCase):
         self.vlan2 = VLAN.objects.create(vid=2, name='Test VLAN 2')
         self.vlan3 = VLAN.objects.create(vid=3, name='Test VLAN 3')
 
+        self.prefix1 = Prefix.objects.create(prefix=IPNetwork('192.168.1.0/24'))
+
     def test_get_vlan(self):
 
         url = reverse('ipam-api:vlan-detail', kwargs={'pk': self.vlan1.pk})
@@ -960,6 +964,20 @@ class VLANTest(APITestCase):
         self.assertHttpStatus(response, status.HTTP_204_NO_CONTENT)
         self.assertEqual(VLAN.objects.count(), 2)
 
+    def test_delete_vlan_with_prefix(self):
+        self.prefix1.vlan = self.vlan1
+        self.prefix1.save()
+
+        url = reverse('ipam-api:vlan-detail', kwargs={'pk': self.vlan1.pk})
+        response = self.client.delete(url, **self.header)
+
+        # can't use assertHttpStatus here because we don't have response.data
+        self.assertEqual(response.status_code, 403)
+
+        content = json.loads(response.content.decode('utf-8'))
+        self.assertIn('detail', content)
+        self.assertTrue(content['detail'].startswith('You tried deleting a model that is protected by:'))
+
 
 class ServiceTest(APITestCase):