fix frontend build.

Author: vangie

.travis.yml

@@ -20,7 +20,7 @@ env:
   - COMMIT=${TRAVIS_COMMIT::8}
   - DOCKER_CACHE_FILE=${HOME}/docker/cache.tar.gz
   - REPO=webide/webide
-  - NODE_ENV=production
+  - NODE_ENV=prod
 
 before_install:
 - sudo apt-get update
@@ -33,7 +33,7 @@ install: true
 
 script:
 - set -e
-- cd frontend && yarn && pwd && ls node_modules/.bin && yarn run build
+- cd frontend && yarn && yarn run build
 - cd ../frontend-webjars && mvn install -DskipTests=true -Dmaven.javadoc.skip=true -B -V
 - cd ../backend && mvn package -DskipTests=true -Dmaven.javadoc.skip=true -B -V
 - cd .. && docker build -f Dockerfile -t $REPO:$COMMIT .