Squash backtraces from Bundler.setup

railties/lib/rails/generators/rails/app/templates/config/boot.rb

@@ -2,8 +2,12 @@
 
 # Set up gems listed in the Gemfile.
 gemfile = File.expand_path('../../Gemfile', __FILE__)
-if File.exist?(gemfile)
+begin
   ENV['BUNDLE_GEMFILE'] = gemfile
   require 'bundler'
   Bundler.setup
-end
\ No newline at end of file
+rescue Bundler::GemNotFound => e
+  STDERR.puts e.message
+  STDERR.puts "Try running `bundle install`."
+  exit!
+end if File.exist?(gemfile)