Merge branch 'label-create-error-messages' into 'master'

Correctly shows label errors in dropdown

## What does this MR do?

Correctly shows any errors in the dropdown when creating a new label

## What are the relevant issue numbers?

Closes #18344 

## Screenshots (if relevant)

![Screen_Shot_2016-06-09_at_09.01.59](/uploads/58dc56b39db20a50adce6f12510025fc/Screen_Shot_2016-06-09_at_09.01.59.png)

See merge request !4553

app/assets/javascripts/labels_select.js.coffee

@@ -95,8 +95,11 @@ class @LabelsSelect
             $newLabelCreateButton.enable()
 
             if label.message?
+              errors = _.map label.message, (value, key) ->
+                "#{key} #{value[0]}"
+
               $newLabelError
-                .text label.message
+                .html errors.join("<br/>")
                 .show()
             else
               $('.dropdown-menu-back', $dropdown.parent()).trigger 'click'