Remove columns that are no longer being used.

db/fixtures/999_topics.rb

@@ -95,3 +95,18 @@ ColumnDropper.drop(
     STDERR.puts "Removing superflous topic columns!"
   }
 )
+
+ColumnDropper.drop(
+  table: 'topics',
+  after_migration: 'RemoveAutoCloseColumnsFromTopics',
+  columns: %w{
+    auto_close_at
+    auto_close_user_id
+    auto_close_started_at
+    auto_close_based_on_last_post
+    auto_close_hours
+  },
+  on_drop: ->(){
+    STDERR.puts "Removing superflous topic columns!"
+  }
+)

db/migrate/20170605014820_remove_auto_close_columns_from_topics.rb

@@ -0,0 +1,9 @@
+class RemoveAutoCloseColumnsFromTopics < ActiveRecord::Migration
+  def up
+    # Defer dropping of the columns until the new application code has been deployed.
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end