Revert "don't error out if there's no Gemfile"

This reverts commit f627008.

Author: hone

lib/language_pack/ruby.rb

@@ -638,8 +638,6 @@ def rake_task_defined?(task)
       out = run("env PATH=$PATH bundle exec #{task_check}")
       if $?.success?
         out.strip == "true"
-      elsif out.include?("No Rakefile found")
-        false
       else
         error(out)
       end