Merge pull request #4632 from gnestor/issue-4585

Upgrade yarn to 1.7.0

appveyor.yml

@@ -6,7 +6,7 @@ matrix:
 
 # environment variables
 environment:
-  nodejs_version: "6.9"
+  nodejs_version: "lts"
   matrix:
     - PYTHON: C:\Miniconda
       PYTHON_VERSION: 2.7