Have a "Snapshot taking Script" and try to promote that build. During the promotion it will throw an exception with

2009-10-24 12:05:50,2 [Thread-280] INFO com.pmease.quickbuild.DefaultBuildEngine - Taking repository snapshots for configuration 'X/Y/Z'...
2009-10-24 12:05:50,2 [Thread-280] ERROR com.pmease.quickbuild.web.BuildHelper - Error promoting build.
    java.lang.RuntimeException: Failed to evaluate below expression:
    mvel:for(repository: current.getInvolvedRepositories()) {
     repository.takeSnapshot();
    }