treechecker shouldn't choke on IOError and other classes

[jmettraux]

22:03 _Taz_: Is there a way to handle "being / rescue / end" block without being shot at by the Rufus tree Checker about global vars?
22:04 jmettraux: ?
22:05 jmettraux: begin/rescue/end has nothing to do with global variables 
22:06 _Taz_: Event with a "rescue IOError => e [...]", with IOError being considered as a global var?
22:07 jmettraux: what is the exact error message you are seeing ?
22:08 _Taz_: /var/lib/gems/1.8/gems/rufus-treechecker-1.0.6/lib/rufus/treechecker.rb:238:in `check': global vars are forbidden (Rufus::SecurityError)
22:08 _Taz_: from /var/lib/gems/1.8/gems/rufus-treechecker-1.0.6/lib/rufus/treechecker.rb:519:in `do_check'
22:08 _Taz_: from /var/lib/gems/1.8/gems/rufus-treechecker-1.0.6/lib/rufus/treechecker.rb:525:in `do_check'
22:08 _Taz_: [... truncated ...]
22:08 _Taz_: from /var/lib/gems/1.8/gems/ruote-2.2.1/lib/ruote/engine.rb:622:in `register_participant'
22:08 _Taz_: from ./rest.rb:334

[jmettraux]

eventually add option to trust any block participant code