ActiveRecord::StatementInvalid:
   sqlite3::sqlException: cannot start a transaction within a transaction: begin transaction

spec_helper.rb中使用的配置是：@H_301_5@

require 'spork'
require 'database_cleaner'

Spork.prefork do
 # .. snip
  RSpec.configure do |config|
   # .. snip
    config.before(:suite) do
      DatabaseCleaner.strategy = :transaction
      DatabaseCleaner.clean_with(:truncation)
    end

    config.before(:each) do
      DatabaseCleaner.start
    end

    config.after(:each) do
      DatabaseCleaner.clean
    end
  end
end

Spork.each_run do

end