Gtk-WARNING **: Locale not supported by C library. Using the fallback 'C' local

[Jumbo]

julio@julio-System-Product-Name:~$ vlc
VLC media player 1.1.12 The Luggage (revision exported)
Blocked: call to unsetenv("DBUS_ACTIVATION_ADDRESS")
Blocked: call to unsetenv("DBUS_ACTIVATION_BUS_TYPE")
[0x967892c] main libvlc: Executando o VLC com a interface padrão. Use 'cvlc' para usar o VLC sem interface.
Blocked: call to setlocale(6, "")
Blocked: call to setlocale(6, "")

(process:14076): Gtk-WARNING **: Locale not supported by C library.
   Using the fallback 'C' locale.
Blocked: call to setlocale(6, "")

O que significa esse warning?