bin/wechat:18:in `with': uninitialized constant App::Helper::YAML (NameE...

 bin/wechat users
bin/wechat:18:in `with': uninitialized constant App::Helper::YAML (NameError)
  from bin/wechat:45:in `users'
  from /Users/john/.rvm/gems/ruby-2.1.2/gems/thor-0.19.1/lib/thor/command.rb:27:in `run'
  from /Users/john/.rvm/gems/ruby-2.1.2/gems/thor-0.19.1/lib/thor/invocation.rb:126:in `invoke_command'
  from /Users/john/.rvm/gems/ruby-2.1.2/gems/thor-0.19.1/lib/thor.rb:359:in `dispatch'
  from /Users/john/.rvm/gems/ruby-2.1.2/gems/thor-0.19.1/lib/thor/base.rb:440:in `start'
  from bin/wechat:138:in `<main>'