Workaround nyc@15

Co-authored-by: raphinesse

appveyor.yml

@@ -8,7 +8,7 @@ environment:
   # - nodejs_version: "4"
 
 matrix:
-  fast_finish: true
+  fast_finish: false
 
   # allow_failures:
   #   - nodejs_version: "4" # for eslint 5
@@ -22,14 +22,10 @@ install:
   # Get the latest stable version of Node.js or io.js
   - ps: Install-Product node $env:nodejs_version
 
+  # Use npm@6.10.3 to work-around issues w/ nyc@<15 on Windows
+  - npm install -g npm@6.10.3;
+
   # install modules
-  - ps: >-
-      if ($env:nodejs_version -eq "4") {
-        npm install -g npm@3;
-      }
-      if ($env:nodejs_version -eq "12") {
-        npm install -g npm@6.10.3;
-      }
   - npm install
 
   # fix symlinks