I get the following error when trying to pipeline build:

org.jenkinsci.plugins.scriptsecurity.sandbox.RejectedAccessException: Scripts not permitted to use staticMethod org.codehaus.groovy.runtime.DefaultGroovyMethods capitalize java.lang.String

It's triggered by the code in my pipeline definition:

def branchToBuild = "${env.JOB_NAME}".tokenize('-').last()
def dockerTaskBranch = branchToBuild.capitalize()

The capitalize method should be safe enough to call from the sandbox