I created _Events.groovy in script directory then added code below:
_Events.groovy
eventConfigureTomcat = {tomcat -> println \"Tomcat.......................
This is a bug and I'm looking into it. It works if you disable fork mode, which you can disable either by deleting the entire grails.project.fork block in BuildConfig.groovy, or by setting the run configuration to false:
grails.project.fork
run
false
grails.project.fork = [ ... run: false ... ]