Prevent middleware error on older Django versions (<1.8) (#603)

Author: wsabransky

contrib/opencensus-ext-django/opencensus/ext/django/middleware.py

@@ -99,7 +99,12 @@ def _set_django_attributes(span, request):
         return
 
     user_id = django_user.pk
-    user_name = django_user.get_username()
+    try:
+        user_name = django_user.get_username()
+    except AttributeError:
+        # AnonymousUser in some older versions of Django doesn't implement
+        # get_username
+        return
 
     # User id is the django autofield for User model as the primary key
     if user_id is not None:

contrib/opencensus-ext-django/tests/test_django_middleware.py

@@ -430,6 +430,43 @@ def test_process_response(self):
 
         self.assertEqual(span.attributes, expected_attributes)
 
+    def test_process_response_no_get_username(self):
+        from opencensus.ext.django import middleware
+
+        trace_id = '2dd43a1d6b2549c6bc2a1a54c2fc0b05'
+        span_id = '6e0c63257de34c92'
+        django_trace_id = '{}/{}'.format(trace_id, span_id)
+
+        django_request = RequestFactory().get('/', **{
+            google_cloud_format._TRACE_CONTEXT_HEADER_NAME: django_trace_id})
+
+        middleware_obj = middleware.OpencensusMiddleware()
+
+        middleware_obj.process_request(django_request)
+        tracer = middleware._get_current_tracer()
+        span = tracer.current_span()
+
+        exporter_mock = mock.Mock()
+        tracer.exporter = exporter_mock
+
+        django_response = mock.Mock()
+        django_response.status_code = 200
+
+        expected_attributes = {
+            'http.url': u'/',
+            'http.method': 'GET',
+            'http.status_code': '200',
+        }
+
+        mock_user = mock.Mock()
+        mock_user.pk = 123
+        mock_user.get_username.side_effect = AttributeError
+        django_request.user = mock_user
+
+        middleware_obj.process_response(django_request, django_response)
+
+        self.assertEqual(span.attributes, expected_attributes)
+
     def test_process_response_unfinished_child_span(self):
         from opencensus.ext.django import middleware