Mailgun: fix webhook error with null delivery-status

Mailgun now sometimes posts `"delivery-status": null` 
in the tracking event payload. Avoid raising an AttributeError
when that occurs.

Fixes #361

CHANGELOG.rst

@@ -44,6 +44,13 @@ Features
   (Thanks to `@Arondit`_ for the implementation.)
 
 
+Fixes
+~~~~~
+
+* **Mailgun:** Avoid an error when Mailgun posts null delivery-status
+  to the event tracking webhook. (Thanks to `@izimobil`_ for the fix.)
+
+
 v10.2
 -----
 
@@ -1595,6 +1602,7 @@ Features
 .. _@Flexonze: https://github.com/Flexonze
 .. _@gdvalderrama: https://github.com/gdvalderrama
 .. _@Honza-m: https://github.com/Honza-m
+.. _@izimobil: https://github.com/izimobil
 .. _@janneThoft: https://github.com/janneThoft
 .. _@jc-ee: https://github.com/jc-ee
 .. _@joshkersey: https://github.com/joshkersey

anymail/webhooks/mailgun.py

@@ -172,12 +172,12 @@ class MailgunTrackingWebhookView(MailgunBaseWebhookView):
 
         try:
             delivery_status = event_data["delivery-status"]
-        except KeyError:
+            # if delivery_status is None, an AttributeError will be raised
-            description = None
-            mta_response = None
-        else:
             description = delivery_status.get("description")
             mta_response = delivery_status.get("message")
+        except (KeyError, AttributeError):
+            description = None
+            mta_response = None
 
         if "reason" in event_data:
             reject_reason = self.reject_reasons.get(

tests/test_mailgun_webhooks.py

@@ -630,6 +630,22 @@ class MailgunTestCase(WebhookTestCase):
         self.assertEqual(event.event_type, "clicked")
         self.assertEqual(event.click_url, "https://example.com/test")
 
+    def test_delivery_status_is_none_event(self):
+        raw_event = mailgun_sign_payload(
+            {
+                "event-data": {
+                    "event": "accepted",
+                    "delivery-status": None,
+                }
+            }
+        )
+        response = self.client.post(
+            "/anymail/mailgun/tracking/",
+            data=json.dumps(raw_event),
+            content_type="application/json",
+        )
+        self.assertEqual(response.status_code, 200)
+
 
 @tag("mailgun")
 @override_settings(ANYMAIL_MAILGUN_WEBHOOK_SIGNING_KEY=TEST_WEBHOOK_SIGNING_KEY)