bundle install 的 gem 提示 cannot load such file

  /usr/local/lib/ruby/site_ruby/2.1.0/rubygems/core_ext/kernel_require.rb:54:in `require': cannot load such file -- sequel (LoadError)
    from /usr/local/lib/ruby/site_ruby/2.1.0/rubygems/core_ext/kernel_require.rb:54:in `require'
    from dna_in.rb:2:in `<main>'

 bundle install 的 gem 如果提示 cannot load such file, 需要使用 bundle exec 执行