Custom 500 error message should only be seen for Preview

lms/djangoapps/certificates/tests/test_webview_views.py

@@ -454,9 +454,13 @@ class CertificatesViewsTests(ModuleStoreTestCase, EventTrackingTestCase):
             user_id=self.user.id,
             course_id=unicode(self.course.id)
         )
-        response = self.client.get(test_url)
+        response = self.client.get(test_url + "?preview=honor")
         self.assertIn("Invalid Certificate Configuration", response.content)
 
+        # Verify that Exception is raised when certificate is not in the preview mode
+        with self.assertRaises(Exception):
+            self.client.get(test_url)
+
     @override_settings(FEATURES=FEATURES_WITH_CERTS_ENABLED)
     def test_certificate_evidence_event_emitted(self):
         self.client.logout()

lms/djangoapps/certificates/views/webview.py

@@ -281,7 +281,10 @@ def _update_certificate_context(context, course, user, user_certificate):
     )
 
 
-@handle_500(template_path="certificates/server-error.html")
+@handle_500(
+    template_path="certificates/server-error.html",
+    test_func=lambda request: request.GET.get('preview', None)
+)
 def render_html_view(request, user_id, course_id):
     """
     This public view generates an HTML representation of the specified student's certificate