class Psych::Visitors::YAMLTree

def dump_exception o, msg
  tag = ['!ruby/exception', o.class.name].join ':'
  @emitter.start_mapping nil, tag, false, Nodes::Mapping::BLOCK
  if msg
    @emitter.scalar 'message', nil, nil, true, false, Nodes::Scalar::ANY
    accept msg
  end
  @emitter.scalar 'backtrace', nil, nil, true, false, Nodes::Scalar::ANY
  accept o.backtrace
  dump_ivars o
  @emitter.end_mapping
end