Currently the install hook for applying the yaml files is being executed in Phase "Prepare" (https://jackrabbit.apache.org/filevault/apidocs/org/apache/jackrabbit/vault/packaging/InstallContext.Phase.html). The reason for that is most probably due to the description in https://jackrabbit.apache.org/filevault/apidocs/org/apache/jackrabbit/vault/packaging/InstallHook.html which states that only from Phase "Prepare" you can throw exceptions which lead to package installation failures.

The drawback of using PREPARE though is that

1. you cannot create/update some initial content through a regular package structure and afterwards set ACLs for those in the same package.
2. You cannot use repository structures as workaround for missing support for global variables (Allow to reuse variables from other YAML files #257)
3. Initial content should be defined as regular content to be able to depend on it for application package type (https://issues.apache.org/jira/browse/JCRVLT-170). Those package types are not allowed to contain uncovered roots!

We should check again if PREPARE is really the only phase where Exception are being properly propagated.