pip certbot package name is old (letsencrypt)

[Hiromasa Ihara]

currently ansible-letsencrypt try to install "letsencrypt" package by pip in unsupported platforms.
but today "letsencrypt" package is renamed to "certbot" and is not updated.

ansible-letsencrypt/tasks/install-with-pip.yml

Line 42 in 12e16bb

 name: letsencrypt 

And In my case, I have some problem related to ↑.
like certbot/certbot#8036 ("letsencrypt" package is not fixed this pr/issue, so execution ansible-letsencrypt was failed.)

[Hiromasa Ihara]

sorry I mistook understanding letsencrypt package.
letsencrypt is virtual package and the contents is same to certbot.
I close this issue.