issue with select2-rails 4.0.0 but select2-rails 3.5.9.3 works

[kevin-jj]

<%= f.select :country_id,options_from_collection_for_select(Country.all,:id,:name, @current_country.id),{:include_blank => true},{:class =>"col-sm-12 country form-group pure-padding","data-rule-required"=>true}%>

It does not show up any error message. Any help would be appreciated.

[kevin-jj]

css conflict.