[python] drop 3.9 support

[isabelizimm]

partially related to #9655. Python 3.9 is EOL and packages like IPython have not released 3.9 compatible versions in a while. To get more modern support, we may want to drop 3.9.

[juliasilge]

We'll want to update our docs here: https://positron.posit.co/install.html

It might also be worth adding a small section (maybe right here?) about how to use Positron with older Python. For example, install ipykernel yourself and change the python.useBundledIpykernel setting? Anything else?

[austin3dickey]

I think that would be about it, yeah. We still can't guarantee support even if you bring your own ipykernel, though. For example, someone trying 3.8 on today's Positron would run into a TypeError on this line, since we use lowercase tuple in the type hint:

positron/extensions/positron-python/python_files/posit/positron/convert.py

Line 79 in 588e8ab

def convert_sorts(self) -> tuple[List[StrictStr], List[StrictStr]]:

Probably BYO would work for a while on 3.9 until someday it doesn't. 🙂

[austin3dickey]

Additional things we could do in the future: have some sort of a deprecation timeline that includes

• marking 3.9 as (Deprecated) instead of (Unsupported)
• continuing testing it, installing ipykernel on the fly

And then after that period of time, actually drop support.