Workaround: open the package contents (right click the .app in Finder), then go to Contents/Resources/locale, rename the "fr" folder to something else and rename "en_GB" (or your preferred language) to "fr".
Workaround: open the package contents (right click the .app in Finder), then go to Contents/ Resources/ locale, rename the "fr" folder to something else and rename "en_GB" (or your preferred language) to "fr".