Comment 4 for bug 560956

I suspect that the problem is related to the fact that "eo.utf8" does not contain an underscore. All other locales in my /usr/lib/locale contain a country specification, such as "CH" in "de_CH.utf8". I remember that we once used "XX" for Esperanto but this XX seems to have gone.

If my assumption is correct then synaptic and/or a ibrary it uses require the underscore in the locale name. The message "wrong language code" suggests that something tries to parse the locale name, taking everything before the underscore as the "language code".

I cannot say if there is a rule saying that locale names must contain an underscore. We could try with an underscore and an empty country code, such as "eo_.utf8". To test my hypothesis I created such a locale in /usr/lib/locales and called synaptic with "LANG=eo_.utf8". No error window. But that does not tell us whose fault the problem is and which side (synaptic or the locale definition) should be changed.