Railsチュートリアル 1.5.1 Herokuのセットアップとデプロイ で「source <(curl -sL https://cdn.learnenough.com/heroku_install)…」ができなかったとき

#環境
AWS cloud9

#詰まった箇所
1.5.1 Herokuのセットアップとデプロイ
手順通り
source <(curl -sL https://cdn.learnenough.com/heroku_install)
を実行したら下記のエラーが出た

cloud9console

ubuntu:~/environment/sample_app (master) $ source <(curl -sL https://cdn.learnenough.com/heroku_install)
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 30.5M  100 30.5M    0     0  26.1M      0  0:00:01  0:00:01 --:--:-- 26.1M
mv: cannot move 'heroku' to '/usr/local/heroku': Directory not empty

ここでHerokuのバージョン確認をした時のコマンド結果を思いだした

cloud9

ubuntu:~/environment/sample_app (master) $ heroku --version

Command 'heroku' not found, but can be installed with:

sudo snap install heroku

sudo snap install herokuを指示通り打ってみた

cloud9

ubuntu:~/environment/sample_app (master) $ sudo snap install heroku
error: This revision of snap "heroku" was published using classic confinement and thus may perform
       arbitrary system changes outside of the security sandbox that snaps are usually confined to,
       which may put your system at risk.

       If you understand and want to proceed repeat the command including --classic.

--classicオプションをつけろと怒られたのでもう一度トライ

cloud9

ubuntu:~/environment/sample_app (master) $ sudo snap install heroku --classic
heroku v7.47.6 from Heroku✓ installed

無事Herokuインストールできました

cloud9

ubuntu:~/environment/sample_app (master) $ heroku -v
 ›   Warning: Our terms of service have changed: https://dashboard.heroku.com/terms-of-service
heroku/7.47.6 linux-x64 node-v12.16.2