generate required attribute for `date_time` input

closes #730

CHANGELOG.md

@@ -1,6 +1,9 @@
 ## 2.1.0.dev
 
 ### enhancements
+  * generate required attribute for `date_time` input.
+    ([@nashby](https://github.com/nashby))
+    Closes [#730](https://github.com/plataformatec/simple_form/issues/730).
   * `grouped_collection_select` now accepts proc/lambda as label and value method.
     ([@svendahlstrand](https://github.com/svendahlstrand))
     Closes [#623](https://github.com/plataformatec/simple_form/issues/623).

lib/simple_form/inputs/date_time_input.rb

@@ -5,10 +5,6 @@ module SimpleForm
         @builder.send(:"#{input_type}_select", attribute_name, input_options, input_html_options)
       end
 
-      def has_required?
-        false
-      end
-
       private
 
       def label_target

test/inputs/datetime_input_test.rb

@@ -91,9 +91,9 @@ class DateTimeInputTest < ActionView::TestCase
     assert_select 'label[for=project_created_at_4i]'
   end
 
-  test 'date time input should not generate invalid required html attribute' do
+  test 'date time input should generate required html attribute' do
     with_input_for @user, :delivery_time, :time, :required => true
     assert_select 'select.required'
-    assert_no_select 'select[required]'
+    assert_select 'select[required]'
   end
 end