DOC: add a brief explanation of build isolation to the tutorial

[rgommers]

Build isolation is a regular cause of confusion for many users, so a brief explanation can't hurt.

Also add a very brief note that the build venv must be activated - the venv docs are confusing here, as gh-630 shows. Closes gh-630

[dnicolodi]

Having a short explanation of the reason why the virtual environment needs to be activated would be beneficial IMO.

[rgommers]

How about adding: (otherwise meson or another executable may not be found).

[rgommers]

This fell through the cracks. I have made the suggested edit now. This should be good to go.

[dnicolodi]

Thanks @rgommers. I wonder whether it is time to have a Building a package top sections in the documentation with the details about build isolation, venv and some hints about cibuildwheel and co for building redistributable wheels.

[rgommers]

Thanks @rgommers. I wonder whether it is time to have a Building a package top sections in the documentation with the details about build isolation, venv and some hints about cibuildwheel and co for building redistributable wheels.

Yes, I agree. This is the cause of a lot of the questions/issues we are receiving. I also just searched for auditwheel and it's not in our docs (except in the non-public explanations/design-old.rst).

I won't be able to work on that in the next few days though, since it'll take a few hours at least to do it right. Should we open a new issue for that first, and scope it? I think I'd prefer to address your one comment here, and then have a new PR for the new docs page, containing:

• The content added here
• Content from design-old.rst
• Mentioning all the relevant tools.
• I'd like to refer to https://pypackaging-native.github.io/meta-topics/build_steps_conceptual/#building-and-installing-or-uploading-artifacts, which explains a lot of things that are relevant here.

[dnicolodi]

I'd prefer to address your one comment here, and then have a new PR for the new docs page

Sure. I didn't want to suggest that it should be done as part of this PR.

[rgommers]

@dnicolodi this is still mergeable I think - mind if I hit the merge button? I'll open the follow-up issue for the separate docs section now.

[dnicolodi]

I would like to find the time for some substantial improvements to the tutorial: I think that now it focuses on the wrong things. But this PR adds useful information and does not hinder future edits. I'm merging it.