try adding force flag

etpinard · etpinard · commit b71d4acac0d2 · 2016-04-04T16:25:34.000-04:00
diff --git a/appveyor.yml b/appveyor.yml
@@ -10,7 +10,7 @@ install:
   - ps: Install-Product node $env:nodejs_version
   - node --version
   - npm --version
-  - npm install
+  - npm install --force
 
 test_script:
   - npm run citest-jasmine -- ie
