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

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I know this is deprecated, but I am doing a course where I have to use this gem instead of ActiveStorage or Carrierwave.

The problem is, in Rails 6.0, whenever I run rails db:{drop,create,migrate} I get:

Dropped database 'db/development.sqlite3'
Dropped database 'db/test.sqlite3'
Created database 'db/development.sqlite3'
Created database 'db/test.sqlite3'
== 20200914221802 CreatePictures: migrating ===================================
-- create_table(:pictures)
   -> 0.0048s
== 20200914221802 CreatePictures: migrated (0.0050s) ==========================

== 20200916062631 DeviseCreateUsers: migrating ================================
-- create_table(:users)
   -> 0.0053s
-- add_index(:users, :email, {:unique=>true})
   -> 0.0019s
-- add_index(:users, :reset_password_token, {:unique=>true})
   -> 0.0040s
== 20200916062631 DeviseCreateUsers: migrated (0.0150s) =======================

== 20200916063812 AddUserIdToPics: migrating ==================================
-- add_column(:pictures, :user_id, :integer)
   -> 0.0048s
== 20200916063812 AddUserIdToPics: migrated (0.0049s) =========================

== 20200916064238 AddUsernameToUsers: migrating ===============================
-- add_column(:users, :username, :string)
   -> 0.0060s
== 20200916064238 AddUsernameToUsers: migrated (0.0062s) ======================

rails aborted!
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:

  class AddAttachmentImageToPics < ActiveRecord::Migration[4.2]
/home/sourav/railsProjects/InstagramApp/db/migrate/20200919075557_add_attachment_image_to_pics.rb:1:in `<main>'
/home/sourav/railsProjects/InstagramApp/bin/rails:9:in `<top (required)>'
/home/sourav/railsProjects/InstagramApp/bin/spring:15:in `<top (required)>'
bin/rails:3:in `load'
bin/rails:3:in `<main>'

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

  class AddAttachmentImageToPics < ActiveRecord::Migration[4.2]
/home/sourav/railsProjects/InstagramApp/db/migrate/20200919075557_add_attachment_image_to_pics.rb:1:in `<main>'
/home/sourav/railsProjects/InstagramApp/bin/rails:9:in `<top (required)>'
/home/sourav/railsProjects/InstagramApp/bin/spring:15:in `<top (required)>'
bin/rails:3:in `load'
bin/rails:3:in `<main>'
Tasks: TOP => db:migrate
(See full trace by running task with --trace)

The issue can be fixed simply by modifying the migration file, and add [6.0] beside ActiveRecord::Migration, for me it's something like this:

class AddAttachmentImageToPics < ActiveRecord::Migration[6.0]
  def self.up
    change_table :pictures do |t|
      t.attachment :image
    end
  end

  def self.down
    remove_attachment :pics, :image
  end
end

And then run:

rails db:environment:set RAILS_ENV=development db:{drop,create,migrate}

This is a temporary fix that has to be followed every time I create migration...