Hammer CLI

Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=1088442
Try creating an activation key using the same name/label as another. A generic "400 bad request" message is printed instead of indicating that the name is already in use (the server log contains this message).

Two fixes probably needed:
1. hammer-cli-foreman does not handle bad request
2. hammer-cli-katello should make sure the 'displayMessage' gets used in the error type (and all the others?)
or
katello needs to return json data in the same format as foreman does ('message'?)