Update kernel's python dependencies

[mcaceresb]

Problem description

The python dependencies, specially those outlined in requirements_dev.txt, are dated. Unit tests (via pytest) are additionally failing. The issue seems to be that python packages have changed slightly over the years (rather than any fundamental problem with the kernel itself). I tried to update the dependencies and discovered it wasn't particularly simple, hence this issue.

Other information

See, for example, #404, #413 (and possibly #409).

NB: Given this wasn't a simple task I may not get to it for some time unless it proves to be a serious issue.

TODO

• Check tests in other OSs.
• Check rest of tests.

[kylebarron]

I now prefer using Poetry for python projects because it supplies an entire lockfile. I can put up a quick PR if you want to see how it works