Error Ruby ('fileutils')

Problema:
Cuando ejecutas la aplicacion y te aparece esto en la terminal:

C:/Ruby200/lib/ruby/2.0.0/fileutils.rb:93: warning: already initialized constant FileUtils::OPT_TABLE
C:/Ruby200/lib/ruby/2.0.0/FileUtils.rb:93: warning: previous definition of OPT_TABLE was here
C:/Ruby200/lib/ruby/2.0.0/fileutils.rb:1272: warning: already initialized constant FileUtils::Entry_::S_IF_DOOR
C:/Ruby200/lib/ruby/2.0.0/FileUtils.rb:1272: warning: previous definition of S_IF_DOOR was here
C:/Ruby200/lib/ruby/2.0.0/fileutils.rb:1533: warning: already initialized constant FileUtils::Entry_::DIRECTORY_TERM
C:/Ruby200/lib/ruby/2.0.0/FileUtils.rb:1533: warning: previous definition of DIRECTORY_TERM was here
C:/Ruby200/lib/ruby/2.0.0/fileutils.rb:1537: warning: already initialized constant FileUtils::Entry_::SYSCASE
C:/Ruby200/lib/ruby/2.0.0/FileUtils.rb:1537: warning: previous definition of SYSCASE was here
C:/Ruby200/lib/ruby/2.0.0/fileutils.rb:1656: warning: already initialized constant FileUtils::LOW_METHODS
C:/Ruby200/lib/ruby/2.0.0/FileUtils.rb:1656: warning: previous definition of LOW_METHODS was here
C:/Ruby200/lib/ruby/2.0.0/fileutils.rb:1662: warning: already initialized constant FileUtils::METHODS
C:/Ruby200/lib/ruby/2.0.0/FileUtils.rb:1662: warning: previous definition of METHODS was here

Solución:
verifica si escribiste todo en minúsculas la librería 'fileutils', sino es así, hacemos los cambios y quedaría de la siguiente manera:
require 'fileutils'