Using libraries from processing-3.0a4 in ruby processing

Up to and including processing-2.2.1 the path to sketchbook was/is discovered by "reading" the preferences.txt configuration file for ruby processing. For processing-3.0a4 the name has changed (to allow different libraries/sketches to co-exist for different versions?). For processing-3.0a4 you can set the "sketchbook_path" in the ".rp5rc" file, works for me on linux see yaml file below (will override preferences.txt value).

---
PROCESSING_ROOT: /home/tux/processing-3.0a4
JRUBY: "true"
sketchbook_path: /home/tux/sketchbook