chore(gitlab-ci): hopefully fix error due to happy version

.gitlab-ci.yml

@@ -6,7 +6,7 @@ workflow:
 
 default:
   image:
-    name: fpco/stack-build:lts-17.2
+    name: fpco/stack-build:lts-16.31
   cache: &global_cache
     paths:
       - node_modules
@@ -118,6 +118,9 @@ yesod:build:dev:
     - install -v -m 0700 -d ~/.ssh
     - install -v -T -m 0644 ${SSH_KNOWN_HOSTS} ~/.ssh/known_hosts
     - install -v -T -m 0400 ${SSH_DEPLOY_KEY} ~/.ssh/deploy && echo "IdentityFile ~/.ssh/deploy" >> ~/.ssh/config; 
+    - stack install happy
+    - export PATH="${HOME}/.local/bin:$PATH"
+    - hash -r
     - git restore-mtime
   artifacts:
     paths: