Handle and report errors with credentials correctly

[ankon]

With an expired credential:

> kubernetes-bootstrap --template-directory templates --output-directory .tmp/development "--kubeconfig" "kube-aws/kubeconfig" "--disable-overrides" "--exclude" "minikube" "-D" "environment=wip/polaris" "-D" "region=eu-west-1" ...
(node:6012) UnhandledPromiseRejectionWarning: #<Object>
(node:6012) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:6012) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

This should be first of all logging the issue correctly ("credentials expired"), and also fail with the correct error code.