A quick way to test localisation is to temporarily set the environment
variable LC_ALL when running the server, e.g.
$ LC_ALL=es_ES.UTF-8 ./src/trip-server
To update the PO files for translation:
$ cd po $ make update-po
After updating the translations, run the same command to re-create the binary files, then install them in the correct location with:
$ make $ sudo make install