To reproduce:
rm plugins/tracker/site-content/tuleap-tracker.pot
make generate-mo
make restart-services (if needed)
Now as user with language = fr,
go to project » trackers » Global tracker administration.
=> you should not have mixed content (en_US & fr_FR)
Introduced by
git #tuleap/stable/ee672d5d53dc917386921302875e63f34358d6cd