Use install Pipenv.

leaveningagent · leaveningagent · commit c0c00c4e18b7 · 2019-05-02T21:14:57.000-07:00
diff --git a/appveyor.yml b/appveyor.yml
@@ -1,6 +1,6 @@
 version: '{build}'
 init:
-    - cmd: pip install pipenv
+    - cmd: pip install -U pipenv
     - cmd: pip install poetry==1.0.0a2
     - ps: npm i -g serverless
 build: off
