ActiveModel::Errors#keys is deprecated and will be removed in Rails 6.2.

[caljess599]

https://github.com/activeadmin-plugins/active_admin_import/blob/90e82de06cc6cfa2af10953a4c9597eac62e6fe6/lib/active_admin_import/import_result.rb#L36

attribute_names is now needed instead.

See [active model's code] (https://github.com/rails/rails/blob/53410537594be0c0a528cff53dce433dd386cb6a/activemodel/lib/active_model/errors.rb#L273) for the specifics