我down了一个divshot的本地环境，在运行jekyll的时候出现如下错误？请问是什么原因？
刚开始根据提示我将ext.rb的第一行 由require ’sprockets‘改为了require "sprockets"运行成功，第二次就不得行了！请指点12.！3Q
Configuration file: /Users/JCNetwork-Mecil9/DivShot/_config.yml
/Users/JCNetwork-Mecil9/DivShot/_plugins/_site/ext.rb:1:in `require': cannot load such file -- sprockets (LoadError)
from /Users/JCNetwork-Mecil9/DivShot/_plugins/_site/ext.rb:1:in `<top (required)>'
from /Library/Ruby/Gems/2.0.0/gems/jekyll-2.5.0/lib/jekyll/plugin_manager.rb:74:in `require'
from /Library/Ruby/Gems/2.0.0/gems/jekyll-2.5.0/lib/jekyll/plugin_manager.rb:74:in `block (2 levels) in require_plugin_files'
from /Library/Ruby/Gems/2.0.0/gems/jekyll-2.5.0/lib/jekyll/plugin_manager.rb:73:in `each'
from /Library/Ruby/Gems/2.0.0/gems/jekyll-2.5.0/lib/jekyll/plugin_manager.rb:73:in `block in require_plugin_files'
from /Library/Ruby/Gems/2.0.0/gems/jekyll-2.5.0/lib/jekyll/plugin_manager.rb:72:in `each'
from /Library/Ruby/Gems/2.0.0/gems/jekyll-2.5.0/lib/jekyll/plugin_manager.rb:72:in `require_plugin_files'
from /Library/Ruby/Gems/2.0.0/gems/jekyll-2.5.0/lib/jekyll/plugin_manager.rb:18:in `conscientious_require'
from /Library/Ruby/Gems/2.0.0/gems/jekyll-2.5.0/lib/jekyll/site.rb:79:in `setup'
from /Library/Ruby/Gems/2.0.0/gems/jekyll-2.5.0/lib/jekyll/site.rb:41:in `initialize'
from /Library/Ruby/Gems/2.0.0/gems/jekyll-2.5.0/lib/jekyll/commands/build.rb:29:in `new'
from /Library/Ruby/Gems/2.0.0/gems/jekyll-2.5.0/lib/jekyll/commands/build.rb:29:in `process'
from /Library/Ruby/Gems/2.0.0/gems/jekyll-2.5.0/lib/jekyll/commands/build.rb:18:in `block (2 levels) in init_with_program'
from /Library/Ruby/Gems/2.0.0/gems/mercenary-0.3.5/lib/mercenary/command.rb:220:in `call'
from /Library/Ruby/Gems/2.0.0/gems/mercenary-0.3.5/lib/mercenary/command.rb:220:in `block in execute'
from /Library/Ruby/Gems/2.0.0/gems/mercenary-0.3.5/lib/mercenary/command.rb:220:in `each'
from /Library/Ruby/Gems/2.0.0/gems/mercenary-0.3.5/lib/mercenary/command.rb:220:in `execute'
from /Library/Ruby/Gems/2.0.0/gems/mercenary-0.3.5/lib/mercenary/program.rb:42:in `go'
from /Library/Ruby/Gems/2.0.0/gems/mercenary-0.3.5/lib/mercenary.rb:19:in `program'
from /Library/Ruby/Gems/2.0.0/gems/jekyll-2.5.0/bin/jekyll:20:in `<top (required)>'
from /usr/local/bin/jekyll:23:in `load'
from /usr/local/bin/jekyll:23:in `<main>'`请输入代码`使用bundle exec jekyll serve这条命令试试