When I want to open Gparted :
sudo gparted
The result is disappointing.

(process:12516): Gtk-WARNING **: Locale not supported by C library.
Using the fallback 'C' locale.
======================
libparted : 2.3
======================
Fontconfig warning: "/etc/fonts/conf.d/50-user.conf", line 9: reading configurations from ~/.fonts.conf is deprecated.

(gpartedbin:12516): glibmm-ERROR **:
unhandled exception (type std::exception) in signal handler:
what: locale::facet::_S_create_c_locale name not valid
How you find this ?