YAML serialization problem for Exception
The implementation of YAML.object_maker allocates an object and
instance_variable_set the instance variables passed as the second
argument, while Exception doesn't seem to use such instance variable to
return the exception message (Exception#message). This bug can be
reproduced by typing
YAML::load(YAML::dump(Exception.new('test_message'))) in IRB.
this bug can be reproduced in Ruby 1.8 as well