I noticed a number of ERROR lines in the hub logs. There were several instances of this:

koji.hub: Error: task 43072584 is non-free but unlocked (state 3)

This is coming from Task.lock() in the hub code. It looks like this is simply a host trying to open a task that has just been canceled. This sort of thing happens regularly, since a task can be canceled between the time that a host queries it and tries to open it.

So...

• I don't think this should be an error message, probably not even a warning
• the code should be more discriminating. The canceled case is not an error, but an open task with no host is probably an error worth complaining about
• The message should be less confusing and more informative

Beyond that, several of the other error messages in this function could stand to be clarified.