Hammer CLI

Hammer defaults to 'base' output adapter if it can't find adapter specified in --output:

hammer --output=unknown user list                                                                                                                                                         
Id:            3
Login:         admin
Name:          Admin User
Email:         root@example.com
Admin:         yes
Last login:    2017/10/20 11:21:39
Authorized by: Internal

Id:            52
Login:         ipa_bob
Name:          Bob Doe
Email:         ipa_bob@ipa.test
Admin:         no
Last login:    2017/07/13 12:36:02
Authorized by: FreeIPA ldap

This is quite confusing behavior, especially when user passes 'yml' instead of the only supported 'yaml'. Both outputs aren't that different at a first glance.

Expected result:
Hammer should end with error instead, informing that the adapter name is unknown and listing the available ones.