Error : an internal rt error has occurred. your administrator can find more details in rt's log files

RTIR
2

Try this:
$ apt-get remove libjson-xs-perl

More info:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=848041
http://lists.fsck.com/pipermail/rt-users/2013-November/082124.html