Description of problem:

I upgraded a notebook running Fedora 26 to Fedora 28.
Prior to the upgrade, the notebook was fully localized in French (fr_FR.utf8).
But after the upgrade, parts of the system are found to be localized in US English.

Version-Release number of selected component (if applicable):
glibc-langpack-fr-2.27-8.fc28.x86_64


How reproducible:
Reproducible.

Steps to Reproduce:
1. Prepare a PC or virtual instance under Fedora 27 or 26
2. Set localization to all French and Paris time zone
3. Upgrade to Fedora 28 thru "dnf system-upgrade"
4. Type the "date" command in a shell window

Actual results:

The date comes back in US English
$ date
Fri May 11 19:37:12 CEST 2018

Expected results:

Date should be in French:
$ date
ven. mai 11 19:38:21 CEST 2018


Additional info:

The behavior of the "date" command persists even after setting the
LANG environment variable explicitely to fr_FR.utf8.

Also some parts of the GUI have been "reverted" to US English.
For example, the top menu "Système" has become "System".

I am using the MATE spin, but there is probably no influence from that.

By tracing the date command with strace, it seems that some files under
/usr/lib/locale/ are missing, such as fr_FR.utf8 ;
and these files are owned by RPM package glibc-langpack-fr.

Turns out this package is NOT installed on the system.

Installing manually the glibc-langpack-fr RPM package is a good workaround,
assuming the user has the appropriate skills.

Of course, one can suspect the same would happen with a notebook localized in Spanish, German, etc....
So something seems amiss in the Fedora system upgrade procedure for non-US systems.

Thanks a lot for your help.