Comment 1 for bug 211974

Agreed, but I believe this bug/fix belongs to the launchpad-buildd code, which is the part that actually blocks, not slave-scanner.

It isn't that simple as it looks, because unpacking the chroot is part of the start_build xmlrpc command and making this call asynchronous will possibly involve postponing this procedure to the build time, i.e. 'start_build' would return after downloading the chroot.

Anyway, this bug exists and I'm more than happy to help you with the implementation.