Yes, the locale message can be ignored.
Looking at the message I would wonder what makes it try to invoke that gjs command (somewhere in another script?). Is it because the path/libpath that are expected aren't the ones that are used under Gimp? Or if you are using a flatpak or snap Gimp installation their virtual filesystem doesn't include the one where the gjs command resides (or map it to their own local file system)?
Looking at the message I would wonder what makes it try to invoke that gjs command (somewhere in another script?). Is it because the path/libpath that are expected aren't the ones that are used under Gimp? Or if you are using a flatpak or snap Gimp installation their virtual filesystem doesn't include the one where the gjs command resides (or map it to their own local file system)?