This reverts commit 5a0e0e72.

This commit causes railties tests on TravisCI to always return a 0 status (all tests passing), even when tests are failing. Reverting for now until a new solution can be found.

This will also get the defaults from attribute definitions like:

     attribute :type, :string, default: "SomethingElse"

`has_attribute?` method to check wether a given attribute has been defined.

This solves the following error:

     ActiveRecord::StatementInvalid: Could not find table 'guitars'

It seems that the table structure of the `Guitar` model has not been
necessary until now. Due to the wrong table name the model was not
correctly linked to the table.

STI cast new instances to `default type` on initialize.

fixes #17121

Update autoloading_and_reloading_constants.md

It appears that I missed this one when I delegated all the non-mutation
array methods that were not on Enumerable

Fixed a typo

Modify unscoped usage guide to include chaining [ci skip]

Explain the connection pool error message better [ci skip]

rescue memcached errors in a consistent way

The previous message was misleading (especially for Ops guys) when
diagnosing problems related to the database connection.

The message was suggesting that the connection cannot be obtained which
normally assumes the need to look at the database.

But this isn't the case as the connection could not be retrieved from
the application's internal connection pool.

The new message should make it more explicit and remove the confusion.

Allow use of minitest-rails gem with test runner

Fix rake db:structure:dump on Postgres when multiple schemas are used

Conflicts:
	activerecord/CHANGELOG.md

Closes #22346.

Refactor `AbstractAdapter#initialize`

Fix indentation in CHANGELOG.md [ci skip]

`pool` in args is unused anymore. And `config` is used in all adapters.

Move some bind related test cases from finder_test.rb to sanitize_t…

Document message validation option accepts Proc [ci skip]

Add `Routing` namespace to point appropriate constant

Bugfix collection association #create method

`connection_options` is only needed for `MysqlAdapter`

Not needed for `Mysql2Adapter` and `AbstractMysqlAdapter`.

Added dollarsign to the README.md for consistancy [ci skip]

[ci skip] add `controller:` argument to routing.md

Fix set_autoload_paths and set_load_path document  [ci skip]

Brush up errors of `ActionDispatch::Routing::Mapper#mount`

[ci skip] Add author's name to CHANGELOG

disable rails minitest extension in rails plugin

* Integrate to raise `ArgumentError`
* Detailed error message when `path` is not defined
* Add a test case, invalid rack app is passed

The failure have returned, so disabling the tests again. (The upgrade is
fine to keep.)