Comment 2 for bug 819674

Phew. Looks like this isn't much of a problem after all. The backup dir gets moved to its working location for processing, and finally gets promoted to the "real" directory once done. If an Exception is caught along the way, it gets kicked back to the backup location. Or if a KeyboardInterrupt occurs along the way, it stays in the working location and the next script run will kick it back to the backup location.

It would be slightly nicer to have this taken care of upon KeyboardInterrupt as well, so people don't wonder where the backup dists dir went. But no biggie.