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

core/modules/aggregator/migration_templates/d6_aggregator_feed.yml

@@ -1,9 +1,9 @@
 id: d6_aggregator_feed
-label: Drupal 6 aggregator feeds
+label: Aggregator feeds
 migration_tags:
   - Drupal 6
 source:
-  plugin: d6_aggregator_feed
+  plugin: aggregator_feed
 process:
   fid: fid
   title: title

core/modules/aggregator/migration_templates/d6_aggregator_item.yml

@@ -1,16 +1,15 @@
 id: d6_aggregator_item
-label: Drupal 6 aggregator items
+label: Aggregator items
 migration_tags:
   - Drupal 6
 source:
-  plugin: d6_aggregator_item
+  plugin: aggregator_item
 process:
   iid: iid
   fid:
     plugin: migration
     migration: d6_aggregator_feed
-    source:
-      - fid
+    source: fid
   title: title
   link: link
   author: author

core/modules/aggregator/migration_templates/d6_aggregator_settings.yml

@@ -1,5 +1,5 @@
 id: d6_aggregator_settings
-label: Drupal 6 aggregator configuration
+label: Aggregator configuration
 migration_tags:
   - Drupal 6
 source:

core/modules/aggregator/migration_templates/d7_aggregator_feed.yml

@@ -0,0 +1,20 @@
+id: d7_aggregator_feed
+label: Aggregator feeds
+migration_tags:
+  - Drupal 7
+source:
+  plugin: aggregator_feed
+process:
+  fid: fid
+  title: title
+  url: url
+  refresh: refresh
+  checked: checked
+  queued: queued
+  link: link
+  description: description
+  image: image
+  etag: etag
+  modified: modified
+destination:
+  plugin: entity:aggregator_feed

core/modules/aggregator/migration_templates/d7_aggregator_item.yml

@@ -0,0 +1,23 @@
+id: d7_aggregator_item
+label: Aggregator items
+migration_tags:
+  - Drupal 7
+source:
+  plugin: aggregator_item
+process:
+  iid: iid
+  fid:
+    plugin: migration
+    migration: d7_aggregator_feed
+    source: fid
+  title: title
+  link: link
+  author: author
+  description: description
+  timestamp: timestamp
+  guid: guid
+destination:
+  plugin: entity:aggregator_item
+migration_dependencies:
+  required:
+    - d7_aggregator_feed

core/modules/aggregator/migration_templates/d7_aggregator_settings.yml

@@ -1,5 +1,5 @@
 id: d7_aggregator_settings
-label: Drupal 7 aggregator configuration
+label: Aggregator configuration
 migration_tags:
   - Drupal 7
 source: