Recent versions of ckeditor will make precompile hang.

[monaka]

I got timeout error when I push master branch to heroku,
My OSX was hanged up while executing bundle exec rake assets:precompile RAILS_ENV=production --trace

I fixed issues above by down-grading ckeditor to 4.0.4.

I found some similar report in the web.
It should be specified gem 'ckeditor', '4.0.4' or something for now.

[GrantRWinter]

Thanks so much Monaka! I was having the exact same issue and this solved it.