Make Rails use full sentences in validation messages.

validation_sentences.rb

module I18n
  module Backend
    module Base
      protected

      def load_file_with_sentences(filename)
        load_file_without_sentences(filename).tap do |data|
          unless Rails.configuration.paths["config/locales"].expanded.include?(filename)
            data.each do |locale, d|
              if d and d.key?("errors")
                if d["errors"].key?("format")
                  store_translations locale, { "errors" => { "format" => "%{message}" } }
                end

                if old = d["errors"]["messages"]
                  new = old.each_with_object({}) { |(k,v),h| h[k] = "%{attribute} #{v}." if v.is_a?(String) }
                  store_translations locale, { "errors" => { "messages" => new } }
                end
              end
            end
          end
        end
      end

      alias_method_chain :load_file, :sentences
    end
  end
end

begin
  RailsAdmin::FormBuilder
rescue NameError
else
  class RailsAdmin::FormBuilder
    def errors_for field
      field.errors.present? ? @template.content_tag(:span, field.errors.first, :class => 'help-inline') : ''
    end
  end
end