Comment # 27 on bug 952855 from Dominique Leuenberger

(In reply to Erwan GEORGET from comment #14)
> Created attachment 654052 [details]
> boxes.log

open("/usr/share/locale-langpack/fr/LC_MESSAGES/gnome-boxes.mo", O_RDONLY) = 11
fstat(11, {st_mode=S_IFREG|0644, st_size=11377, ...}) = 0
mmap(NULL, 11377, PROT_READ, MAP_PRIVATE, 11, 0) = 0x7ff029e61000

It makes no sense that this file is being found on your system... this should,
imho, be -ENOENT

Can you please check, using rpm -qf
/usr/share/locale-langpack/fr/LC_MESSAGES/gnome-boxes.mo, what own this file?

For a test, you can try to move this file out of the way (keep a backup). and
retry...