can't pass coursera's grader

[]["You don't have bcrypt installed in your application. Please add it to your Gemfile and run bundle install\n", "rake aborted!\n", "LoadError: cannot load such file -- bcrypt\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:274:in `require'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:274:in `block in require'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:238:in `block in load_dependency'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:647:in `new_constants_in'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:238:in `load_dependency'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:274:in `require'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activemodel-4.2.3/lib/active_model/secure_password.rb:58:in `has_secure_password'\n", "/home/railsuser/app/app/models/user.rb:5:in `<class:User>'\n", "/home/railsuser/app/app/models/user.rb:1:in `<top (required)>'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:457:in `load'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:457:in `block in load_file'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:647:in `new_constants_in'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:456:in `load_file'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:354:in `require_or_load'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:494:in `load_missing_constant'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:184:in `const_missing'\n", "/home/railsuser/app/db/seeds.rb:29:in `<top (required)>'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:268:in `load'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:268:in `block in load'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:240:in `load_dependency'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:268:in `load'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/railties-4.2.3/lib/rails/engine.rb:547:in `load_seed'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activerecord-4.2.3/lib/active_record/tasks/database_tasks.rb:250:in `load_seed'\n", "/usr/local/rvm/gems/ruby-2.2.2/gems/activerecord-4.2.3/lib/active_record/railties/databases.rake:180:in `block (2 levels) in <top (required)>'\n", "/usr/local/rvm/gems/ruby-2.2.2/bin/ruby_executable_hooks:15:in `eval'\n", "/usr/local/rvm/gems/ruby-2.2.2/bin/ruby_executable_hooks:15:in `<main>'\n", "Tasks: TOP => db:seed\n", "(See full trace by running task with --trace)\n"]