fix AP warning; remove unused variable

actionpack/lib/action_controller/metal/live.rb

@@ -34,6 +34,7 @@ module ActionController
   module Live
     class Buffer < ActionDispatch::Response::Buffer #:nodoc:
       def initialize(response)
+        @error_callback = nil
         super(response, SizedQueue.new(10))
       end
 

activerecord/lib/active_record/railties/databases.rake

@@ -373,7 +373,7 @@ namespace :railties do
         puts "NOTE: Migration #{migration.basename} from #{name} has been skipped. Migration with the same name already exists."
       end
 
-      on_copy = Proc.new do |name, migration, old_path|
+      on_copy = Proc.new do |name, migration|
         puts "Copied migration #{migration.basename} from #{name}"
       end