It seems like gettext only searches for locale information in /usr/share/locale, by default. I installed ikiwiki into /usr/local, therefore the locale information wasn't found. This patch fixes the issue:

--- a/
+++ b/
@@ -1057,6 +1057,7 @@ sub gettext {
                                return shift;
+                       $gettext_obj->dir("$installdir/share/locale/");
                return $gettext_obj->get(shift);

-- ?ThomasBleher

According to my testing, this patch makes ikiwiki's localisation fail for LANG=fr_FR when everything is installed to the default locations, though LANG=es_ES works. I don't understand this behavior, especially since strace shows it successfully opening the file /usr/share/locale/fr/LC_MESSAGES/

(Also, it should check that $installdir is set before using it.)