Use pipx for installation of mathlibtools

[TwoFX]

This is my attempt at the most likely abandoned #74, trying to address the fact that using sudo pip3 install seems to be discouraged (cf. this comment). The easiest way of installing end-user software from PyPI that follows "best practices" that I am aware of is pipx, which in particular has a command ensurepath that does all the PATH fiddling (which is not necessary when using sudo, but is necessary when using --user) automatically. This PR changes the instructions to follow this route.

[dimpase]

I'd have mentioned what pipx does, e.g.

(along with a support tool [pipx](https://pipxproject.github.io/pipx/))

[TwoFX]

I'd have mentioned what pipx does, e.g.

(along with a support tool [pipx](https://pipxproject.github.io/pipx/))

Good point. I've added this and also took the liberty to slightly homogenize the different guides.

[semorrison]

Sadly, this doesn't work. I just followed the instructions on a fresh Windows 10 machine, and upon getting to this step pipx install mathlibtools just says bash: pipx: command not found.

I closed and restarted "git bash", and get the same message. I rebooted the windows machine (I have not yet tried unplugging the router...) and get the same message.

[TwoFX]

Thank you for testing this. I'm looking into it.

[dimpase]

pipx is known to work on Windows, so the question is about what goes wrong in your environment. Something semi-trivial with PATH, I suppose. Hard to tell without a Windows box (or at least a VM) in front of me.

[TwoFX]

The first problem is that pipx ensurepath modifies the Windows PATH variable, but we want to modify the git bash PATH, which is different.

After manually setting the path, there was also some venv problem, which can probably be fixed, but I didn't try very hard.

[TwoFX]

Despite pipx documentation claiming that it works on Windows, I was unable to confirm that this is indeed the case, so I decided to roll back the changes. Global pip install doesn't require administrator privileges on Windows anyway, the difference between global and user install is merely whether the package is installed to AppData/Local (global) or AppData/Roaming (User), so personally I think manually having the user figure out the correct path (which includes both the user name and the Python version number) is not worth it. I have also rolled back the changes to macos.md; while i believe that it should work similar to Linux (replacing apt with brew), I have no way to verify this.

[PatrickMassot]

@TwoFX am I correct in thinking that instructions in this PR now match what is done by the automatic scripts, hence work? Could you have a look at the git conflict?

[TwoFX]

@TwoFX am I correct in thinking that instructions in this PR now match what is done by the automatic scripts, hence work?

Yes the instructions match.

Could you have a look at the git conflict?

I merged; is the conflict resolved?

[PatrickMassot]

Actually, the conflicts were due to the complicated git history. The end result was not conflicting, so I squashed. Thanks again for looking into all this.