Make AppVeyor happy

Author: harpocrates

appveyor.yml

@@ -6,7 +6,7 @@ environment:
   matrix:
     # - resolver: lts-6.35 # ghc-7.10.3
     # - resolver: lts-7.24 # ghc-8.0.1
-    - resolver: lts-9.21 # ghc-8.0.2
+    # - resolver: lts-9.21 # ghc-8.0.2
     - resolver: lts-10.7 # ghc-2.2.2
     - resolver: nightly
 
@@ -25,5 +25,5 @@ build_script:
   - stack --no-terminal install --resolver %resolver% alex
 
 test_script:
-  - stack --no-terminal test --resolver %resolver% :unit-tests
+  - stack --no-terminal test --resolver %resolver% :unit-tests --test-arguments "--plain"