Remove duplicated HashWithIndifferentAccess#with_indifferent_access.
implement ActiveRecord::Base#pretty_print + changelog
Test `except!` in other cases too
Fix AS::NumberHelper results with rationals

:precision was incorrectly being applied to Rationals

before:
  ActiveSupport::NumberHelper.number_to_rounded Rational(10, 3), precision: 2
  => "3.3"
after:
  ActiveSupport::NumberHelper.number_to_rounded Rational(10, 3), precision: 2
  => "3.33"
Test the serialized types of virtual columns in XML

The previous tests were passing, because nothing ever looked at the
generated XML. What was previously being generated was
`<firstname type="NilClass">...`, which is not consistent with all other
cases where there is not a known type.
Refactor XML serializer to not depend on `serialized_attributes`
Update documentation to reflect unsubscription with name.
Avoid looping through subscribers when unsubscribing with a subscriber object.
Merge pull request #15464 from tgxworld/improve_notifications_logic

Improvements to ActiveSupport::Notifications.
Merge pull request #15379 from xuanxu/rational_precision

Fix AS::NumberHelper results with rationals
just use `assert`
File.exist? instead of File.exists? in bin/setup

File.exists? is deprecated in Ruby 2.1+

https://github.com/ruby/ruby/blob/v2_1_2/file.c#L1413
Add missing colon to internal
Remove unused `initialize_attributes` method

This was previously a hook for a special case related to `serialize`,
which has since been removed.
Merge pull request #15473 from sgrif/sg-missing-colon

Add missing colon to internal [ci skip]
Merge pull request #15474 from unixmonkey/master

File.exist? instead of File.exists? in bin/setup
Fix typo in ActionController Overview

* Should say "sensitive" instead of "sensible"
Merge pull request #15477 from aripollak/actioncontroller-overview-typo

Fix typo in ActionController Overview
concat is a hotspot (via AV#append=), so just directly define the methods
Merge pull request #15475 from sgrif/sg-initialize-attributes

Remove unused `initialize_attributes` method