REPL brittleness

[gilch]

See #2.

Jupyter makes this weirdly awkward in a venv. It wants global kernelspecs. Install that if you want, but that seems like overkill when trying out a REPL in a venv. You can start a kernel without installing it, and connect to the most recently started one. But getting these to connect up reliably and automatically in one command is surprisingly difficult. The current solution works, but not reliably. Sometimes it starts the kernel but fails to connect. Sometimes the first error crashes the console. Can't seem to reproduce that one.

Quitting is also awkward. I'm worried about accidentally leaving kernels running in the background, using up resources, and possibly stealing connections later. It also seems to be possible to exit the kernel without quitting the console, which leaves you with a broken console.

No showstoppers, but no easy fixes, and it just doesn't work as well as it should.