I had this exact problem, and I just figured out what was going wrong.
It turned out to be that I'd passed a nonexistent file to "--part" in my vmbuilder command. (In the bug-reporter's case -- I'm not sure whether --part accepts relative paths or not, but if you're sure that vmbuilder.partition exists, you might try specifying the *full path* to that file.)
So as I understand it, this problem arises from user error in specifying the "--part" argument. HOWEVER -- there is still a bug here -- the vmbuilder script tries to be helpful with a warning message, but it ends up falling over and dying because it tries to print the message via a nonexistent attribute. So instead of a warning message, the user gets a cryptic exception backtrace.
I had this exact problem, and I just figured out what was going wrong.
It turned out to be that I'd passed a nonexistent file to "--part" in my vmbuilder command. (In the bug-reporter's case -- I'm not sure whether --part accepts relative paths or not, but if you're sure that vmbuilder.partition exists, you might try specifying the *full path* to that file.)
So as I understand it, this problem arises from user error in specifying the "--part" argument. HOWEVER -- there is still a bug here -- the vmbuilder script tries to be helpful with a warning message, but it ends up falling over and dying because it tries to print the message via a nonexistent attribute. So instead of a warning message, the user gets a cryptic exception backtrace.