ActiveRecord::Errors best practices?

I'm currently reviewing some old code from Rails 1.x times and found
this:

  ActiveRecord::Errors.default_error_messages = {
    :inclusion => "inclusion|",
    :exclusion => "exclusion|",
    :invalid => "invalid|",
    :confirmation => "confirmation|",
    :accepted => "accepted|",
    :empty => "empty|",
    :too_long => "too_long|",
    :too_short => "too_short|",
    :wrong_length => "wrong_length|",
    :taken => "taken|",
    :not_a_number => "not_a_number|",
  }

Used on controller code to check if a specific error happens, like this:

if @user.errors.on("email").to_s.include? "taken|"
  ...
end

Are there better practices for doing this?