Phusion Passenger on Ubuntu not seeing plugin in vendors directory

Question

Phusion Passenger, running on Ubuntu Hardy Heron, is bombing on a require 'lingua/en/readability'. The plugin is installed in the plugins directory and works fine with script/server, just not Passenger.

Error Message:

source file that the application requires, is missing.

*
  It is possible that you didn't upload your application files correctly. Please check whether all your application files are uploaded.
*
  A required library may not installed. Please install all libraries that this application requires.

Further information about the error may have been written to the application's log file. Please check it in order to analyse the problem.

Error message: no such file to load -- lingua/en/readability (MissingSourceFile)

Answer 1

Apparently the plugin needs to be installed on the server. It won't work from a Rails plugin directory as-is.