尝试将ActiveRecord与Sinatra一起使用,迁移失败问题

运行Sinatra1.0时,我想在程序中添加一个数据库表。在我的耙里我有一个任务

task :environment do   
    ActiveRecord::Base.establish_connection(YAML::load(File.open('config/database.yml'))["development"])      
end

我的命名空间中有一个迁移任务调用迁移代码:

    namespace :related_products do  
      desc "run any migrations we may have in db/migrate"
      task :migrate => :environment do   
        ActiveRecord::Migrator.migrate('db/migrate', ENV["VERSION"] ? ENV["VERSION"].to_i : nil )   
    end 

当调用ActiveRecord::Migrator.Migrate()时,控制台会弹出一个错误。 耙子流产了! nil:nilclass的未定义方法“info”

迁移代码本身非常简单…并没有任何线索告诉我这个丢失的信息类是什么。

    class CreateStores < ActiveRecord::Migration
      def self.up       
        create_table :stores do |t|
          t.string :name
          t.string :access_url
          t.timestamps
        end
      end

      def self.down
        drop_table :stores
      end
    end  

我有点迷惑不解,我在寻找一些可能是什么问题的线索。谢谢!

一个简单的回溯显示,攻击线只是对迁移的调用:

    rake aborted!
undefined method `info' for nil:NilClass
/Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record/migration.rb:473:in `migrate'
/Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record/migration.rb:472:in `each'
/Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record/migration.rb:472:in `migrate'
/Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record/migration.rb:400:in `up'
/Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record/migration.rb:383:in `migrate'
/Users/baz/Documents/workspace/rp/Rakefile:26
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in `call'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in `execute'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in `each'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in `execute'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:597:in `invoke_with_call_chain'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:590:in `invoke_with_call_chain'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:583:in `invoke'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2051:in `invoke_task'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `each'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2023:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2001:in `run'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:1998:in `run'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/bin/rake:31
/usr/bin/rake:19:in `load'
/usr/bin/rake:19