Try to serialize circeci

.circleci/config.yml

@@ -129,9 +129,15 @@ jobs:
             tox -e py35
 workflows:
   version: 2
-  build_and_test:
+  build:
     jobs:
       - build-python3.6
-      - build-python2.7
-      - build-python3.4
-      - build-python3.5
+      - build-python2.7:
+          requires:
+            - build-python3.6
+      - build-python3.4:
+          requires:
+            - build-python2.7
+      - build-python3.5:
+          requires:
+            - build-python3.4