class ActiveRecord::Migration::CheckPending

loading a web page if config.active_record.migration_error is set to :page_load
This class is used to verify that all migrations have been run before

def call(env) 

def call(env)
  mtime = ActiveRecord::Migrator.last_migration.mtime.to_i
  if @last_check < mtime
    ActiveRecord::Migration.check_pending!
    @last_check = mtime
  end
  @app.call(env)
end

def initialize(app) 

def initialize(app)
  @app = app
  @last_check = 0
end