我遇到了在Debian 7上安装Redmine 3的麻烦。我跟着this tutorial，即使它是Debian 8.我自己编译了Ruby（v2.3.3）和passenger。
每当我尝试访问redmine URL时，我都会看到一条错误消息，我在Apache2日志中发现了这一点：
[ 2016-12-02 23:15:33.7373 9218/7f42704b4700 age/
Cor/App/Implementation.cpp:304 ]: Could not spawn process for application /opt/redmine: An error occurred while starting up the preloader.
Error ID: e27a0051
Error details saved to: /tmp/passenger-error-LnpIIA.html
Message from application: cannot load such file -- io/wait (LoadError)
/usr/local/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
/usr/local/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
/usr/local/lib/ruby/2.3.0/socket.rb:4:in `<top (required)>'
/usr/local/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
/usr/local/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
/usr/local/lib/ruby/gems/2.3.0/gems/passenger-5.0.30/src/ruby_supportlib/phusion_passenger/ruby_core_enhancements.rb:30:in `<top (required)>'
/usr/local/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
/usr/local/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
/usr/local/lib/ruby/gems/2.3.0/gems/passenger-5.0.30/src/ruby_supportlib/phusion_passenger.rb:235:in `require_passenger_lib'
/usr/local/lib/ruby/gems/2.3.0/gems/passenger-5.0.30/src/helper-scripts/rack-preloader.rb:77:in `init_passenger'
/usr/local/lib/ruby/gems/2.3.0/gems/passenger-5.0.30/src/helper-scripts/rack-preloader.rb:155:in `<module:App>'
/usr/local/lib/ruby/gems/2.3.0/gems/passenger-5.0.30/src/helper-scripts/rack-preloader.rb:30:in `<module:PhusionPassenger>'
/usr/local/lib/ruby/gems/2.3.0/gems/passenger-5.0.30/src/helper-scripts/rack-preloader.rb:29:in `<main>'
由于我对Ruby和Redmine不是很熟悉，有人可以解释我如何解决这个问题？