Once you run scons in your IMP source directory, it is hard to get the source directory back into a state where you can do an out of source build, and, in general, the easiest is to simply check IMP out again. In addition, the failure modes when attempting an out of source build are rather odd. Since quite a number of people have run into this problem, and in-source builds of IMP are not something we want to encourage, I'd like to change the behavior a bit: - make the repository argument required. You can use "." if you want to do an in-source build - print an error message and terminate the build immediately with a message to the effect that "You should do an out of source build. If you, for some reason, really want to do an in-source build, add repository=. to your config."

Seem reasonable?