couldn't find file 'formtastic_ie6' with type 'text/css'

[hww]

Following the REAME.md there is error in the line i--- e6.css file

/*
*= require formtastic_ie6
*/

What I do wrong?

There is the log

couldn't find file 'formtastic_ie6' with type 'text/css'
Checked in these paths: 
  /home/valery/projects/veda/tc-tech-platform/tc-tech-server/app/assets/config
  /home/valery/projects/veda/tc-tech-platform/tc-tech-server/app/assets/images
  /home/valery/projects/veda/tc-tech-platform/tc-tech-server/app/assets/stylesheets
  /home/valery/.local/share/gem/ruby/3.2.0/gems/jquery-rails-4.5.1/vendor/assets/javascripts
  /home/valery/.local/share/gem/ruby/3.2.0/gems/stimulus-rails-1.2.1/app/assets/javascripts
  /home/valery/.local/share/gem/ruby/3.2.0/gems/turbo-rails-1.3.3/app/assets/javascripts
  /home/valery/.local/share/gem/ruby/3.2.0/gems/importmap-rails-1.1.5/app/assets/javascripts
  /home/valery/.rvm/gems/ruby-3.2.0/gems/actiontext-7.0.4.2/app/assets/javascripts
  /home/valery/.rvm/gems/ruby-3.2.0/gems/actiontext-7.0.4.2/app/assets/stylesheets
  /home/valery/.rvm/gems/ruby-3.2.0/gems/actioncable-7.0.4.2/app/assets/javascripts
  /home/valery/.rvm/gems/ruby-3.2.0/gems/activestorage-7.0.4.2/app/assets/javascripts
  /home/valery/.rvm/gems/ruby-3.2.0/gems/actionview-7.0.4.2/lib/assets/compiled
  /home/valery/projects/veda/tc-tech-platform/tc-tech-server/app/javascript
  /home/valery/projects/veda/tc-tech-platform/tc-tech-server/vendor/javascript
  /home/valery/.local/share/gem/ruby/3.2.0/gems/popper_js-2.11.6/assets/javascripts
  /home/valery/.local/share/gem/ruby/3.2.0/gems/bootstrap-5.2.3/assets/stylesheets
  /home/valery/.local/share/gem/ruby/3.2.0/gems/bootstrap-5.2.3/assets/javascripts