Directly inheriting from ActiveRecord::Migration is not supported

[palkerecsenyi]

This error occurs when trying to run rails db:migrate after installing advert_selector:

StandardError: An error has occurred, this and all later migrations canceled:

Directly inheriting from ActiveRecord::Migration is not supported. Please specify the Rails release the migration was written for.

This issue can easily be fixed by changing the first line of all three migrations to be:

class CreateAdvertSelector... < ActiveRecord::Migration[5.0]

...rather than...

class CreateAdvertSelector... < ActiveRecord::Migration