Jupyter Notebook instructions

[Nils Bruin]

I noticed that our instructions to install jupyter kernels have fallen out of date a bit. It refers to the instructions available on

https://doc.sagemath.org/html/en/installation/launching.html#setting-up-sagemath-as-a-jupyter-kernel-in-an-existing-jupyter-notebook-or-jupyterlab-installation

in particular:

ln -s $(sage -sh -c 'ls -d $SAGE_VENV/share/jupyter/kernels/sagemath') $HOME/.local/share/jupyter/sagemath-dev

should probably be "...jupyter/kernels/sagemath-dev" (note the inserted "kernels")

Furthermore, the line

ln -s $(sage -sh -c 'ls -d $SAGE_ROOT/venv/share/jupyter/kernels/sagemath') $HOME/.local/share/jupyter/sagemath-dev

doesn't seem to work anymore (and probably needs the same treatment as above in its target: that's not the location where the kernel lives anymore in the source tree. What would be the right location to point at?

(the problem being that `$SAGE_VENV` will change value if sage updates its python version. When that happens, your personal kernel installation now points at the wrong/old/now non-existent venv.)

[Matthias Koeppe]

That's already fixed in https://trac.sagemath.org/ticket/34756