I at least cleaned up the rogue ReaderException that SnakeYAML was raising without warning, but I'm no closer to solving this one.
We should prepare a patch for SnakeYAML to declare ReaderException as a ParserException subclass, or something similar.
~/projects/jruby $ jruby --1.9 -S gem install wirb
Psych::SyntaxError: special characters are not allowed
parse at org/jruby/ext/psych/PsychParser.java:257
parse_stream at /Users/headius/projects/jruby/lib/ruby/1.9/psych.rb:148
parse at /Users/headius/projects/jruby/lib/ruby/1.9/psych.rb:119
load at /Users/headius/projects/jruby/lib/ruby/1.9/psych.rb:106