Ubuntu 20.04にpython-virtualenvがない、でも何とかJitsi Meetサーバをインストールする方法

Ｑ
---
[jitsi meet の構築記録](https://qiita.com/ysaito8015@github/items/5d672705cce61f30fe96)を参考に、素のUbuntu 20.04に[Jitsi Meet](https://meet.jit.si/)サーバをインストールしようとしたら、
[Let's Encrypt](https://letsencrypt.org/ja/)のTSL証明書取得プロセスでエラーが出てしまった。

**E: パッケージ 'python-virtualenv' にはインストール候補がありません**


```shell-session
$ sudo /usr/share/jitsi-meet/scripts/install-letsencrypt-cert.sh
-------------------------------------------------------------------------
This script will:
- Need a working DNS record pointing to this machine(for domain 【FQDN】)
- Download certbot-auto from https://dl.eff.org to /usr/local/sbin
- Install additional dependencies in order to request Let’s Encrypt certificate
- If running with jetty serving web content, will stop Jitsi Videobridge
- Configure and reload nginx or apache2, whichever is used
- Configure the coturn server to use Let's Encrypt certificate and add required deploy hooks
- Add command in weekly cron job to renew certificates regularly

You need to agree to the ACME server's Subscriber Agreement (https://letsencrypt.org/documents/LE-SA-v1.1.1-August-1-2016.pdf) 
by providing an email address for important account notifications
Enter your email and press [ENTER]: 【メールアドレス】
Bootstrapping dependencies for Debian-based OSes... (you can skip this with --no-bootstrap)
ヒット:1 http://jp.archive.ubuntu.com/ubuntu focal InRelease
取得:2 http://jp.archive.ubuntu.com/ubuntu focal-updates InRelease [107 kB]    
取得:3 http://jp.archive.ubuntu.com/ubuntu focal-backports InRelease [98.3 kB] 
ヒット:4 http://ppa.launchpad.net/openjdk-r/ppa/ubuntu focal InRelease         
ヒット:5 http://security.ubuntu.com/ubuntu focal-security InRelease            
ヒット:6 https://download.jitsi.org stable/ InRelease                          
205 kB を 1秒 で取得しました (138 kB/s)
パッケージリストを読み込んでいます... 完了
パッケージリストを読み込んでいます... 完了
依存関係ツリーを作成しています                
状態情報を読み取っています... 完了
注意、'python' の代わりに 'python-is-python2' を選択します
注意、'python-dev' の代わりに 'python-dev-is-python2' を選択します
パッケージ python-virtualenv は使用できませんが、別のパッケージから参照されます。
これは、パッケージが欠落しているか、廃止されたか、または別のソース
からのみ利用可能であることを意味します。

E: パッケージ 'python-virtualenv' にはインストール候補がありません
```

Ａ
---
python-virtualenvの代わりに[Certbot](https://certbot.eff.org/)を使えばいいです。

```shell-session
$ sudo apt install certbot
$ sudo sed -i 's/\.\/certbot-auto/certbot/g' /usr/share/jitsi-meet/scripts/install-letsencrypt-cert.sh
$ sudo ln -s /usr/bin/certbot /usr/sbin/certbot
$ sudo /usr/share/jitsi-meet/scripts/install-letsencrypt-cert.sh
-------------------------------------------------------------------------
This script will:
- Need a working DNS record pointing to this machine(for domain 【FQDN】)
- Download certbot-auto from https://dl.eff.org to /usr/local/sbin
- Install additional dependencies in order to request Let’s Encrypt certificate
- If running with jetty serving web content, will stop Jitsi Videobridge
- Configure and reload nginx or apache2, whichever is used
- Configure the coturn server to use Let's Encrypt certificate and add required deploy hooks
- Add command in weekly cron job to renew certificates regularly

You need to agree to the ACME server's Subscriber Agreement (https://letsencrypt.org/documents/LE-SA-v1.1.1-August-1-2016.pdf) 
by providing an email address for important account notifications
Enter your email and press [ENTER]: 【メールアドレス】
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator webroot, Installer None
Obtaining a new certificate
Performing the following challenges:
http-01 challenge for 【FQDN】
Using the webroot path /usr/share/jitsi-meet for all unmatched domains.
Waiting for verification...
Cleaning up challenges
Running deploy-hook command: /etc/letsencrypt/renewal-hooks/deploy/0000-coturn-certbot-deploy.sh
Output from deploy-hook command 0000-coturn-certbot-deploy.sh:
Configuring turnserver


IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/【FQDN】/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/【FQDN】/privkey.pem
   Your cert will expire on 2020-08-22. To obtain a new or tweaked
   version of this certificate in the future, simply run certbot
   again. To non-interactively renew *all* of your certificates, run
   "certbot renew"
 - If you like Certbot, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le

Configuring nginx
```

参考
---
[Install Jitsi Meet on Ubuntu 20.04 – Self-Hosted Video Conferencing](https://www.vultr.com/docs/install-jitsi-meet-on-ubuntu-20-04-lts#Step_8__Install_Let_s_Encrypt_SSL_Certificate)