Use shutil.rmtree over shelling out to rm -rf in noxfile

[FollowTheProcess]

I was looking through the older issues to try and find the low hanging fruit to close off and found #298.

This PR addresses point 1:

1. Change rm -rf to shutil.rmtree.

I did some digging around points 2 and 3, it would seem that point 2 at least has been resolved anyway (see here).

2. Change the Python version to 3.7 because sphinx-autobuild, which relies on tornado, no longer works on Windows on 3.8.

Point 3 I'm not too sure and I don't have access to a Windows machine to easily test but since we build the official project docs in an ubuntu image on CI I don't see a major issue here?

3. Sphinx fails to follow the reference to changelog and contributing.

Unrelated, but I also noticed that on my machine (macos, python 3.10) running bare nox results in ugly looking failures because it tries to run conda-tests and I don't have conda installed. A simple switch should fix this:

nox.options.sessions = ["tests", "cover", "blacken", "lint", "docs"]
if shutil.which("conda"):
    nox.options.sessions.append("conda_tests")

I'll raise that in a separate issue/PR though to keep things clean 👍🏻

[cjolowicz]

LGTM :)

[cjolowicz]

Point 3 I'm not too sure and I don't have access to a Windows machine to easily test but since we build the official project docs in an ubuntu image on CI I don't see a major issue here?

3. Sphinx fails to follow the reference to changelog and contributing.

@FollowTheProcess I'm wondering if this problem can be solved by enabling symlink support on Windows?

It would be nice to allow contributors on Windows to build the docs without too much hassle.

[FollowTheProcess]

@cjolowicz Ahh I see it's because those documents are symlinked into the docs? I'm not sure to be honest, I haven't been on a Windows machine for a long time!