An initialiser to prevent app to bootstrap app on dev env if pending migrations - cover Rails 3 or newer

00_pending_migrations.rb

## Place in config/initializers/00_pending_migrations.rb

# Raise an error and abort the run there are any pending migrations:
if Rails.env.development?
  # Rails 4 way ;)
  if Rails.version >= '4'
    ActiveRecord::Migration.check_pending!
  else
    # Rails 3 way - TODO: remove when we up to Rails 4
    migrator = ActiveRecord::Migrator.new(
      :up, ActiveRecord::Migrator.migrations_paths
    )
    if (pending = migrator.pending_migrations).any?
      warning = <<-EOF
        Attention! The following migrations are PENDING:
        #{pending.map(&:filename).join("\n")}
        Please run 'rake db:migrate'...
      EOF

      raise warning
    end
  end
end