rails-buildpack:2.6 fails apt-get update because of the certificate issue of letsencrypt.
$ docker run -ti degica/rails-buildpack:2.6 bash
# apt-get update
Hit:1 http://deb.debian.org/debian buster InRelease
Hit:2 http://security.debian.org/debian-security buster/updates InRelease
Ign:3 https://deb.nodesource.com/node_10.x buster InRelease
Hit:4 http://deb.debian.org/debian buster-updates InRelease
Err:5 https://deb.nodesource.com/node_10.x buster Release
Certificate verification failed: The certificate is NOT trusted. The certificate chain uses expired certificate. Could not handshake: Error in the certificate verification. [IP: 23.192.45.81 443]
Reading package lists... Done
E: The repository 'https://deb.nodesource.com/node_10.x buster Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
rails-buildpack:2.6 fails
apt-get update
because of the certificate issue of letsencrypt.This issue is reported at https://github.com/nodesource/distributions/issues/1266 and a workaround in a comment will solve the issue.