Adapt setup instructions for externally managed Python versions

[Ivan-Velickovic]

Homebrew and newer versions of Debian and Ubuntu do not allow you to simply pip install anymore. Since these Python dependencies are available via apt or brew we have to setup a virtual environment.

I chose to leave the pip install instructions since there are still distros and current versions of Ubuntu that are fine with it. Also the default macOS Python via xcode command line utils is fine with pip install. Not sure if it'll just lead to more confusion though.

I'm having issues with building the docs site so whoever reviews should also check that the rendered pages seems sane.

[Indanz]

I haven't build the webpage yet, I'll do that later, have to go soon.

[Indanz]

Is that a one time operation, or do you need to do this every time after logging in?

If you need to do that every time to activate a Python environment I'd separate it and say that explicitly. And assuming venv is the name of the environment, wouldn't it be clearer to have "seL4" as part of its name?

[lsf37]

I'm not sure I'm a fan of this whole venv thing, but I guess there is not really a better way.

I still do have many questions, most of these because I don't really understand how to use these environments more globally.

Do we really need the instructions 3 times? Can we have one venv that works for all of these or are we really installing the dependencies 3 times?

Which directory do we assume people are in when they are running these commands? Do you have to activate the environment each time you want to do any development? Is it local to each repo?

How bad would it be to recommend --break-system-packages?

[Ivan-Velickovic]

Do we really need the instructions 3 times? Can we have one venv that works for all of these or are we really installing the dependencies 3 times?

Yes sure, I guess I did it like this because what you do depends on the context (e.g some people only using seL4 would follow the one for sel4-deps, those using CAmkES follow the one doing camkes-deps.

I also don't really like the venv thing.

I didn't go with --break-system-packages because sel4-deps uses things like PyYAML and lxml which people might already have installed versions of.

I guess we could let the user decide? Doing pip3 install --break-system-packages would be the same behaviour as current Python environments that just let you pip3 install to my knowledge so adding that might not be so bad.

None of the solutions seem ideal.

[Ivan-Velickovic]

(whoops, didn't meant to close).