Currently, running ``application credential show`` on a
non-existent appcred will exit normally and display a
formatted application credential with no data, despite
the Keystone API returning a 404.
Ensure that querying a non-existent application
credential raises an exception message and an exit-code
1 to the user.
Closes-Bug: #2126565
Change-Id: I597d2d4064f1020c5ac40862ecc556f3c94b53eb
Signed-off-by: Matt Anson <matta@stackhpc.com>
fb8cdd4441