Same issue here (KDE). Apparently a bug was opened, then closed by someone who doesn't think a bug can exist if it didn't occur to him:
Backtrack 5 - Bug #36: Setting up dradis (2.7.0-bt2) ... - Redmine
I've never heard of the 'bundle' command, and google hits suggest it's some kind of ruby/rails thing which I'd rather not waste brain cells on.
I also have another VM with the GNOME version (just to prove I'd hate it) and don't have the error. Perhaps it was due to my apt upgrade process. Who knows. Anyway, yea, this sucks.
OK, here's the solution (hopefully this gets posted. For some reason my posts aren't showing up):
The dradis install depends on sourcing /root/.bash_rc. Yes, I know, this is stupid. The solution is to run apt-get upgrade after sourcing this file or within bash.
I guess we forgot to read the fine print that we have to love bash and no shell shall replace it.