while developing I noticed the following bug as well (#179), and it made the service.deregister method returning False without any additional information.
By debugging the code I could see that consul actually returned a 405 (method not allowed) that isn't caught in CB.__status.

Even if #179 will be fixed I thought it could be useful to handle all the 4xx status code (in a generic manner) in CB.__status. I'll submit a PR shortly