Do not raise exception on books which are not consumable offline

[mkb79]

The Complete Book of Five Rings is in fact not available at all. My guess is that it was part of the free audible subscription, but is no longer contained within the description, but still in my library. I would recommend that audible_cli does not print out the stack-trace in this case, but instead a logging message telling the user about the inaccessibility of the item.

Originally posted by @devvythelopper in #235