get context catches 403s, returns a context with no user

admin/main.py

@@ -26,10 +26,14 @@ def get_context(session):
     if 'oauth_user' in session and 'oauth_token' in session:
         admin_client = AdminAPI(app.config['STAGECRAFT_HOST'],
                                 session['oauth_token']['access_token'])
-        context = {
-            'user': session['oauth_user'],
-            'data_sets': admin_client.list_data_sets()
-        }
+        try:
+            context = {
+                'user': session['oauth_user'],
+                'data_sets': admin_client.list_data_sets()
+            }
+        except requests.exceptions.RequestException as e:
+            if not e.response.status_code == 403:
+                raise
     context['environment'] = environment_dict()
 
     return context

tests/admin/test_main.py

@@ -3,7 +3,9 @@
 from admin import app
 from hamcrest import assert_that, equal_to, ends_with
 from httmock import urlmatch, HTTMock
-from mock import patch
+from mock import patch, Mock
+import requests
+from admin.main import get_context
 
 
 @urlmatch(netloc=r'[a-z]+\.development\.performance\.service\.gov\.uk$')
@@ -80,3 +82,40 @@ def test_requires_authentication_continues_when_auth_on_upload_error(
         with HTTMock(performance_platform_status_mock):
             response = self.app.get("/upload-error")
         assert_that(response.status_code, equal_to(200))
+
+    @patch('requests.get')
+    def test_get_context_returns_no_user_or_datasets_on_403(
+            self,
+            mock_get_request):
+        bad_response = requests.Response()
+        bad_response.status_code = 403
+        mock_get_request.return_value = bad_response
+        session_context = get_context({
+            'oauth_token': {
+                'access_token': 'token'},
+            'oauth_user': 'a user'})
+        assert_that(session_context, equal_to({
+            'environment': {
+                'human_name': 'Development',
+                'name': 'development'}}))
+
+    @patch('requests.get')
+    def test_get_context_returns_user_and_datasets_on_200(
+            self,
+            mock_get_request):
+        good_response = requests.Response()
+        good_response.status_code = 200
+        mock_json = Mock()
+        mock_json.return_value = json.dumps({})
+        good_response.json = mock_json
+        mock_get_request.return_value = good_response
+        session_context = get_context({
+            'oauth_token': {
+                'access_token': 'token'},
+            'oauth_user': 'a user'})
+        assert_that(session_context, equal_to({
+            'environment': {
+                'human_name': 'Development',
+                'name': 'development'},
+            'data_sets': '{}',
+            'user': 'a user'}))