firefox-locale-oc software package provides Transitional package for unavailable language, you can install in your Ubuntu 17.04 (Zesty Zapus) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install firefox-locale-oc
firefox-locale-oc is installed in your system.
Make ensure the firefox-locale-oc package were installed using the commands given below,
$ sudo dpkg-query -l | grep firefox-locale-oc *
You will get with firefox-locale-oc package name, version, architecture and description in a table
| Distro | Ubuntu 17 04 zesty zapus |
| Section | Web Software |
| Package | firefox-locale-oc |
| Version | 49.0+build4-0ubuntu2 |
| Description | Transitional package for unavailable language |
| Sub Section | web |