undefined method `assets'

[Mohammed Ammar Kurabi]

Hi,
I am new to ROR

I used rails_db in other project and it works fine, however the gem reporting the following error:

/usr/local/rvm/gems/ruby-2.3.0/gems/railties-5.0.1/lib/rails/railtie/configuration.rb:95:in method_missing': undefined method assets' for #Rails::Application::Configuration:0x0000000431c9d8 (NoMethodError)

Note that I am using ruby 2.3 and rails 5.0.1
I am building and API Back-End
rails new <app_name> --api

Thanks

[Igor Kasyanchuk]

without assets it won't work.
because gem in required to have assets to build the UI