try setting path manually

Author: masci

Diff for: appveyor.yml

@@ -9,12 +9,12 @@ skip_branch_with_pr: true
 
 environment:
   GOPATH: c:\gopath
-  # add protoc, gopath and override default Python 2.7
-  PATH: c:\protoc\bin;$(GOPATH)\bin;C:\Python37;C:\Python37\Scripts;$(PATH)
 
 stack: go 1.12
 
 install:
+  # override default Python 2.7
+  - set PATH=C:\Python37;C:\Python37\Scripts;$(PATH)
   # install the task executor
   - curl -o task.zip -LO https://github.com/go-task/task/releases/download/v2.6.0/task_windows_amd64.zip
   - 7z e task.zip -o$(GOPATH)\bin
@@ -30,6 +30,8 @@ install:
   - 7z e protoc.zip -o$(GOPATH)
 
 test_script:
+  # add protoc, gopath and override default Python 2.7
+  - set PATH=c:\protoc\bin;$(GOPATH)\bin;C:\Python37;C:\Python37\Scripts;$(PATH)
   - task.exe test-integration
 
 # uncomment to debug builds