The following commit adapts the return statements from both lister and their
associated tasks. This standardizes on what other modules (e.g. both dvcs and
package loaders) do.
It's apparently unnecessary as the listener seems to do what's necessary
already  (but it misses tests).
One could argue that having workers (lister, loader, cooker)'s code aligned
would be better in that regard (Note that we could also go the other way
Well, as i started this, might as well propose it...