Currently, repo2docker does not work on Ubuntu 20.04. If you run the repository tests on Ubuntu 20.04, they will fail.
Also, it seems that some dependencies are missing when one runs python3 -m pip install jupyter-repo2docker on Ubuntu 18.04. The tests in the repo2docker repository install some packages that are not installed together with repo2docker by running pip install.
It does seem to be related to the expired cert and an outdated version of ca-certificates in the buildpack-deps:bionic image. You may be able to resolve this by pulling a new version of buildpack-deps:bionic, which was updated 9 hours ago.
ca-certificates 20210119~18.04.2 apparently blacklists the expired DST Root CA X3 certificate.
In my cached version of buildpack-deps:bionic used by repo2docker, the version was 20210119~18.04.1 prior to pulling.
Err:3 https://deb.nodesource.com/node_14.x bionic Release
Certificate verification failed: The certificate is NOT trusted. The certificate chain uses expired certificate. Could not handshake: Error in the certificate verification. [IP: 104.124.58.146 443]
```
I think I will add it ass issue to the bindewrhub.
I was seeing this issue running repo2docker locally and updating buildpack-deps:bionic seemed to solve it. If it’s also happening on mybinder.org then maybe the old image is still cached on their servers? Sorry if I misunderstood the original issue.