Add new CircleCI config which also runs checks under Python 3.

.circleci/config.yml

@@ -112,7 +112,8 @@ jobs:
 
 workflows:
   version: 2
-  build_test_deploy:
+  # Workflow which runs on each push
+  build_test_deploy_on_push:
     jobs:
       - build_and_test_python27
       - build_and_test_python36
@@ -122,3 +123,18 @@ workflows:
           filters:
             branches:
               only: master
+  build_test_weekly:
+    jobs:
+      - build_and_test_python27
+      - build_and_test_python36
+    # Workflow which runs nightly - note we don't perform deploy job on nightly
+    # build
+    triggers:
+      # Run nightly build for the pack
+      - schedule:
+          # NOTE: We run it at 1 am UTC on every Saturday
+          cron: "0 1 * * 6"
+          filters:
+            branches:
+              only:
+                - master