Escaped characters in launch button nbgitpuller URLs

[sean-fitzpatrick]

I am building my first Jupyter book, which is a compilation of some Python-based calculus labs I've written for teaching over the last couple of years. Previously I hosted these as individual Jupyter notebooks on GitHub, and distributed to students using nbgitpuller links. We have a Jupyter hub that is part of the PIMS Syzygy network in Canada.

Usually when I generate an nbgitpuller link (using the nbgitpuller link generator, all the forward slashes in the GitHub URL are escaped. For example, I could have the following URL (requires institutional login):
https://uleth.syzygy.ca/jupyter/hub/user-redirect/git-pull?repo=https%3A%2F%2Fgithub.com%2Fsean-fitzpatrick%2FCalcLabs&urlpath=tree%2FCalcLabs%2FLab1-Intro-to-Python.ipynb&branch=main

I've set up the repository and lauch_buttons sections in my _config.yml file. When I build my Jupyter book, the corresponding URL in the launch button is:
https://uleth.syzygy.ca/jupyter/hub/user-redirect/git-pull?repo=https%3A//github.com/sean-fitzpatrick/CalcLabs&urlpath=tree/CalcLabs/Lab1-Intro-to-Python.ipynb&branch=main

The difference is that after the repo= part of the URL, none of the forward slashes are escaped with %2F.

The first (escaped) URL works properly on our Jupyter hub. The second does not.

Is there a way to configure the build so that characters in the repo URL are escaped?
If not, is this an issue with how our Jupyter hub is configured? I don't manage the hub, but I can submit a request.