How to trick the Ubuntu version as seen by an application?

The key is /etc/lsb-release.

I just modify /etc/lsb-release and make things work. I didn't know about that file before but /etc/issue. However, In my understanding, /etc/issue file is used for shell greeting message and /etc/issue.net file is for remote shell greeting. (FIXME)

I figure it out with strace lsb_release -a and found that it read /etc/lsb-release file.