common.utils.context_processor: Check user attr existence in request

Fix the numerous "'WSGIRequest' object has no attribute 'user'" error
reported in production.

swh/web/common/utils.py

@@ -247,7 +247,11 @@ def context_processor(request):
     in all swh-web templates.
     """
     config = get_config()
-    if request.user.is_authenticated and not hasattr(request.user, "backend"):
+    if (
+        hasattr(request, "user")
+        and request.user.is_authenticated
+        and not hasattr(request.user, "backend")
+    ):
         # To avoid django.template.base.VariableDoesNotExist errors
         # when rendering templates when standard Django user is logged in.
         request.user.backend = "django.contrib.auth.backends.ModelBackend"

swh/web/tests/auth/test_views.py

@@ -15,6 +15,7 @@ from swh.web.auth.models import OIDCUser
 from swh.web.auth.utils import OIDC_SWH_WEB_CLIENT_ID
 from swh.web.common.utils import reverse
 from swh.web.tests.django_asserts import assert_template_used, assert_contains
+from swh.web.urls import _default_view as homepage_view
 
 from . import sample_data
 from .keycloak_mock import mock_keycloak
@@ -326,3 +327,12 @@ def test_oidc_silent_refresh_failure(client, mocker):
         "logout", query_params={"next_path": next_path, "remote_user": 1}
     )
     assert response["location"] == logout_url
+
+
+def test_view_rendering_when_user_not_set_in_request(request_factory):
+    request = request_factory.get("/")
+    # Django RequestFactory do not set any user by default
+    assert not hasattr(request, "user")
+
+    response = homepage_view(request)
+    assert response.status_code == 200