require 'dispatcher'

RE: Plugins for redmine 2.0.1 - Error no such file to load -- dispatcher - 由 Etienne Massip 在 超过一年 之前添加

According to the discussion in #11035, you should try to change the plugin init.rb code from:

require 'dispatcher'

Dispatcher.to_prepare do 
  
end

to something like:

ActionDispatch::Callbacks.to_prepare do 
  
end