Update to drupal 8.0.0-rc1. For more information, see https://www.drupal.org/node/2582663

core/modules/language/config/install/language.entity.en.yml

@@ -1,7 +1,8 @@
+langcode: en
+status: true
+dependencies: {  }
 id: en
 label: English
-direction: 'ltr'
+direction: ltr
 weight: 0
 locked: false
-status: true
-langcode: en

core/modules/language/config/install/language.entity.und.yml

@@ -1,7 +1,8 @@
+langcode: en
+status: true
+dependencies: {  }
 id: und
 label: 'Not specified'
-direction: 'ltr'
-weight: 1
+direction: ltr
+weight: 2
 locked: true
-status: true
-langcode: en

core/modules/language/config/install/language.entity.zxx.yml

@@ -1,7 +1,8 @@
+langcode: en
+status: true
+dependencies: {  }
 id: zxx
 label: 'Not applicable'
-direction: 'ltr'
-weight: 2
+direction: ltr
+weight: 3
 locked: true
-status: true
-langcode: en

core/modules/language/config/optional/tour.tour.language-add.yml

@@ -1,7 +1,9 @@
-id: language-add
-module: language
-label: 'Adding languages'
 langcode: en
+status: true
+dependencies: {  }
+id: language-add
+label: 'Adding languages'
+module: language
 routes:
   - route_name: language.add
 tips:

core/modules/language/config/optional/tour.tour.language-edit.yml

@@ -1,7 +1,9 @@
-id: language-edit
-module: language
-label: Editing languages
 langcode: en
+status: true
+dependencies: {  }
+id: language-edit
+label: 'Editing languages'
+module: language
 routes:
   - route_name: entity.configurable_language.edit_form
 tips:

core/modules/language/config/optional/tour.tour.language.yml

@@ -1,7 +1,9 @@
-id: language
-module: language
-label: Language
 langcode: en
+status: true
+dependencies: {  }
+id: language
+label: Language
+module: language
 routes:
   - route_name: entity.configurable_language.collection
 tips:
@@ -34,7 +36,7 @@ tips:
     body: '<p>You can change the default language of the site by choosing one of your configured languages as default. The site will use the default language in situations where no choice is made but a language should be set, for example as the language of the displayed interface.</p>'
     weight: 4
     attributes:
-      data-class: form-item-site-default-language
+      data-class: js-form-item-site-default-language
   language-operations:
     id: language-operations
     plugin: text