DataMapper multiple Contexts: Error Case

gistfile1.rb

#!/usr/bin/env ruby
#

require 'rubygems'
require 'data_mapper'

class Feed
  include DataMapper::Resource

  property :id,    Serial
  has n, :posts, :through => Resource
  has n, :failed_posts, :through => Resource
end

class Post
  include DataMapper::Resource

  property  :id,          Serial
  has 1, :feed, :through => Resource
  has 1, :conversion
end


class FailedPost
  include DataMapper::Resource

  property  :id,          Serial
  property  :title,       Text, :required => true
  has 1, :feed, :through => Resource
end


class Conversion
  include DataMapper::Resource
  property  :id,        Serial
  belongs_to    :post
end


class RssModel
  attr_reader :our_context
  
  def initialize(option={})
    path = option[:path]
    our_context = option[:context]
    our_context ||= :default      # if none provided, context is :default
    DataMapper.setup(our_context, "#{path}")
    DataMapper.repository(our_context) {
      DataMapper.finalize
      DataMapper.auto_upgrade!
      }
  end
end

src_model=RssModel.new(:path => "sqlite://tmp/testdb.sqlite")
dest_model=RssModel.new(:path => "postgres://user:password@localhost/testdb", :context => :dest_db)