Set config.active_model.i18n_customize_full_message = true

Enables better error message customization

config/application.rb

@@ -35,6 +35,8 @@ module OpenStreetMap
     # Enable locale fallbacks for I18n (makes lookups for any locale fall back to
     # the I18n.default_locale when a translation cannot be found).
     config.i18n.fallbacks = true
+    # Enables custom error message formats
+    config.active_model.i18n_customize_full_message = true
 
     # Use logstash for logging if required
     if Settings.key?(:logstash_path)