File to import not found or unreadable: bootstrap-sprockets on rails 5.2.0

I have following problem. "File to import not found or unreadable: bootstrap-sprockets."

Following gems I have installed
gem 'bootstrap' gem 'bootstrap-sass', '~> 3.3.7'
gem 'sass-rails', '>= 3.2'

File: Application name change from css to scss. In the application.scss file I add the lines

@import "bootstrap-sprockets";
@import "bootstrap";

I bundle install and afterwards restart the server. But still the same error message. It will be great if somebody had the same issue and found a solution, all written solutions on stackoverflow doesn't work.