1 files changed, 23 insertions, 4 deletions
diff --git a/guides/rails_guides.rb b/guides/rails_guides.rb
index ab890f202c..9d1d5567f6 100644
--- a/guides/rails_guides.rb
+++ b/guides/rails_guides.rb
@@ -5,7 +5,7 @@ $:.unshift pwd
 def bundler?
   # Note that rake sets the cwd to the one that contains the Rakefile
   # being executed.
-  File.exists?('Gemfile')
+  File.exist?('Gemfile')
 end
 
 begin
@@ -22,13 +22,32 @@ end
 
 begin
   require 'redcarpet'
-rescue Gem::LoadError
+rescue LoadError
+  # This can happen if doc:guides is executed in an application.
+  $stderr.puts('Generating guides requires Redcarpet 3.1.2+.')
+  $stderr.puts(<<ERROR) if bundler?
+Please add
+
+  gem 'redcarpet', '~> 3.1.2'
+
+to the Gemfile, run
+
+  bundle install
+
+and try again.
+ERROR
+  exit 1
+end
+
+begin
+  require 'nokogiri'
+rescue LoadError
   # This can happen if doc:guides is executed in an application.
-  $stderr.puts('Generating guides requires Redcarpet 2.1.1+.')
+  $stderr.puts('Generating guides requires Nokogiri.')
   $stderr.puts(<<ERROR) if bundler?
 Please add
 
-  gem 'redcarpet', '~> 2.1.1'
+  gem 'nokogiri'
 
 to the Gemfile, run