Change most tests to make use of assert_raise returning the raised
exception rather than relying on a combination of flunk + rescue to
check for exception types/messages.

In Minitest, the second argument of assert_raise(s) accepts a string as
the message that should be shown in case of a failure in the assertion
(eg nothing was raised when it should), and not the exception message to
be matched.

To do that we need to save the exception returned from assert_raise(s)
into a local variable and check for the exception message using it.

Add information about 'available_locales' and 'enforce_available_locales'
to the configuring guide.

Closes #13202. [ci skip]

Fix PostgreSQL range tests on fresh DB

Correcting the name of the table we're creating is self-explanatory.

But we must also move away from the low IDs, because we're not touching the freshly-created primary key sequence; when the time comes, @new_range will be assigned an ID of 1.

fix typos and grammar mistake [ci skip]

set encoding UTF-8 for accepting multibyte character

Fix typo: data --> date [ci-skip]

Change all `MiniTest` to `Minitest`

The changes in c4044b2f meant the tests would error on a fresh DB.

Fix to_param when attribute has multibyte character

/cc @pixeltrix

Assigning nil to a polymorphic belongs_to would nullify its _id field by
not its _type field.

Fixes failing test from c141dfc8.
Regression from 1678e959.

duplication removed(DRY)

Fix typo [ci skip]

change to DateTime.civil_from_format from DateTime.civil_from_fromat in ...

[ci skip]

Ref: https://github.com/seattlerb/minitest/blob/master/History.txt

#none documentation updated [ci skip]

Annotated tags will provide us with Tagger and Time information.

allow video_tag to accept `size` as `Number` for square shaped videos

typo: should be 'DateTime.civil_from_format' and not 'DateTime.civil_from_fromat'

Prettify the removals from Action Controller in 4.1 release notes. [ci skip]