release: 0.20.0

[davidhewitt]

With Python 3.12 out the door and so many improvements ready to ship on our end, I think it's time to push 0.20 live.

There are still a few PRs which I would like to see merged before we release:

• disable marshal.rs on Py_LIMITED_API #3490 - trivial bugfix
• support python 3.12 #3488
• error on passing arguments to #[new] and similar attributes #3484 - small UX improvement which is technically breaking
• also use PyErr::SetObject on Python versions before 3.12 #3455 - a bugfix which makes exceptions chain so I'd prefer ship in a feature release rather than a follow-up patch

Once we have either merged or closed those PRs I will rebase this and prepare to ship.

Closes #3246

[mejrs]

Speaking of Python 3.12, it'd be nice to render the docs with Python 3.12 installed. We can't do much about the docs.rs docs (that is stuck on 3.10) but we should be able to have it on https://pyo3.rs

[davidhewitt]

Reading the netlify documentation it sounds like the Python version available on their builder is very limited, however we could probably move to a Github action where we build the site using 3.12 and then push it with the netlify CLI.

e.g. https://github.com/netlify/actions/tree/master/cli

[davidhewitt]

Now that all of the PRs above have been merged (plus a couple of extra fixes) I have rebased this.

Given there's already been a bit of cooling off here and it's a good day for me to release (I'll be at EuroRust the next couple of days so will be able to find time to support any bugfixes needed), I plan to push this live this evening unless I hear reason to delay.

[davidhewitt]

Ok I found a reason to wait in #3506 🙈

[davidhewitt]

... and I've rebased the fix for that in now, thanks @mejrs. I'm still intending to push this evening :)

[davidhewitt]

Release is live! 🚀