Actually, this ticket has 2 issues:

1. The variable name is hostname not HOSTNAME
2. The nested scope property resolution issue, which, yes, should no longer be an issue in (the upcoming) Groovy 2.4.7. Here's a test case to show it works using 2.4.7-SNAPSHOT: https://github.com/yihtserns/test-logback-gaffer-groovy-247/blob/master/src/test/java/com/github/yihtserns/test/logback/gaffer/groovy247/HostnamePropertyTest.java