update deps

Dockerfile

@@ -1,9 +1,21 @@
-FROM ruby:2.3
+FROM ruby:2.4
 
 WORKDIR /usr/src/app/
 
 # see http://stackoverflow.com/questions/38453963/gitlab-ci-setup-error-could-not-find-a-javascript-runtime
 RUN apt-get update && apt-get install nodejs -y
 
+# set locale
+RUN apt-get install -y locales
+RUN dpkg-reconfigure locales && \
+  locale-gen C.UTF-8 && \
+  /usr/sbin/update-locale LANG=C.UTF-8
+RUN echo 'en_US.UTF-8 UTF-8' >> /etc/locale.gen && \
+  locale-gen
+ENV LC_ALL C.UTF-8
+ENV LANG en_US.UTF-8
+ENV LANGUAGE en_US.UTF-8
+
+# install gems
 COPY Gemfile /usr/src/app/
 RUN bundle install