webhooks: Make MissingHTTPEventHeaderError a WebhookError.

Specifically, an AnomalousWebhookPayloadError.

zerver/lib/webhooks/common.py

@@ -15,7 +15,12 @@ from zerver.actions.message_send import (
     check_send_stream_message_by_id,
     send_rate_limited_pm_notification_to_bot_owner,
 )
-from zerver.lib.exceptions import ErrorCode, JsonableError, StreamDoesNotExistError
+from zerver.lib.exceptions import (
+    AnomalousWebhookPayloadError,
+    ErrorCode,
+    JsonableError,
+    StreamDoesNotExistError,
+)
 from zerver.lib.request import RequestNotes
 from zerver.lib.send_email import FromAddress
 from zerver.lib.timestamp import timestamp_to_datetime
@@ -61,7 +66,7 @@ def notify_bot_owner_about_invalid_json(
     )
 
 
-class MissingHTTPEventHeaderError(JsonableError):
+class MissingHTTPEventHeaderError(AnomalousWebhookPayloadError):
     code = ErrorCode.MISSING_HTTP_EVENT_HEADER
     data_fields = ["header"]
 

zerver/tests/test_webhooks_common.py

@@ -185,11 +185,13 @@ class MissingEventHeaderTestCase(WebhookTestCase):
     # an actual webhook, instead of just making a mock
     def test_missing_event_header(self) -> None:
         self.subscribe(self.test_user, self.STREAM_NAME)
-        result = self.client_post(
-            self.url,
-            self.get_body("ticket_state_changed"),
-            content_type="application/x-www-form-urlencoded",
-        )
+        with self.assertLogs("zulip.zerver.webhooks.anomalous", level="INFO") as webhook_logs:
+            result = self.client_post(
+                self.url,
+                self.get_body("ticket_state_changed"),
+                content_type="application/x-www-form-urlencoded",
+            )
+        self.assertTrue("Missing the HTTP event header 'X-Groove-Event'" in webhook_logs.output[0])
         self.assert_json_error(result, "Missing the HTTP event header 'X-Groove-Event'")
 
         realm = get_realm("zulip")