-class SubscribeAuthorsToDiaryEntries < ActiveRecord::Migration[5.0]
+class SubscribeAuthorsToDiaryEntries < ActiveRecord::Migration[4.2]
def up
DiaryEntry.find_each do |diary_entry|
diary_entry.subscriptions.create(:user => diary_entry.user) unless diary_entry.subscribers.exists?(diary_entry.user.id)