[backintime] sr_Latn: can't guess language

Hello,
I am upstream maintainer of Back In Time [1]. The Debian Tracker system 
gives me an error about the sr_Latn.po file [2].

I checked several official lists and would say that "sr_Latn" is a usual 
and standardized identifier.

My Debian Package maintainer is not responsive to anything. Two other 
persons involved in the packaging have very limited ressources. So I am 
asking you how to handle the problem and if I can fix something at 
upstream to solve the problem?

Regards,
Christian

[1] -- <https://github.com/bit-team/backintime>
[2] -- <https://i18n.debian.org/l10n-pkg-status/b/backintime.html>