Add locales to the image and set it to en_GB out of the box.

Override the LC_ALL, LANGUAGE, LANG, locale-gen environment
variables if you want a different locale.

8.0/Dockerfile

@@ -11,6 +11,8 @@ RUN set -x; \
             npm \
             python-support \
             python-pyinotify \
+            locales-all \
+            locales \
         && npm install -g less less-plugin-clean-css \
         && ln -s /usr/bin/nodejs /usr/bin/node \
         && curl -o wkhtmltox.deb -SL http://nightly.odoo.com/extra/wkhtmltox-0.12.1.2_linux-jessie-amd64.deb \
@@ -35,6 +37,11 @@ COPY ./entrypoint.sh /
 COPY ./openerp-server.conf /etc/odoo/
 RUN chown odoo /etc/odoo/openerp-server.conf
 
+RUN locale-gen en_GB.UTF-8
+ENV LANG en_GB.UTF-8
+ENV LANGUAGE en_GB:en
+ENV LC_ALL en_GB.UTF-8
+
 # Mount /var/lib/odoo to allow restoring filestore and /mnt/extra-addons for users addons
 VOLUME ["/var/lib/odoo", "/mnt/extra-addons"]