GitLab upgrade completed. Current version is 17.11.1. We now benefit from the features of the release 17.11.
The Binder as defined in May 2021 no longer worked (due to an issue from Xeus-cling - their demo Binder no longer works as well).
But modifying it with the compiler hint provided by Nicolas Thierry works: https://github.com/jupyter-xeus/xeus-cling/issues/413
I also moved the environment.yml file into a directory which makes its use more obvious, following suggestion from repo2docker documentation.
Solves #38 (closed)