jruby-complete shades the yecht.jar which contains the yaml ruby files for MRI-1.8.x

when you have classpath:/ or uri:classloader:/ then those files are used instead of stdlib ones. the yecht files are outdated and do not even match the files from ./lib/ruby/1.8

not sure if this all is of practical implication beside it sidetracked by finding #3306

i.e. better exclude those from jruby-complete