Python 3.9 support (and upcoming incompatibility with cpython 3.7 and 3.8)

[bdraco]

Brief description

With Python 3.9 entering more wider production it would be nice to get a 2.4.5 release to solve the following issue which has already been fixed:

46fa40f

Environment

• Scapy version: 2.4.4
• Python version: 3.9
• Operating System: Alpine Linux

[bdraco]

Also it looks like 3.8 and 3.7 will have the issue in the next release since https://bugs.python.org/issue41976 is backported

python/cpython#22598
python/cpython#22600
python/cpython#22601

[bdraco]

https://bugs.python.org/issue42580#msg387117

The issue was closed in the python bug tracker so its unlikely it will get resolved there.

[guedou]

This sounds like a fair request.

@gpotter2 @p-l- do you have some features that you want to implement before releasing 2.4.5?

[p-l-]

@guedou I don't, I wanted the new Net() / Net6() implementations, so that's all set for me!

[polybassa]

If it is possible, I would be very happy if I could get #3075 and #3078 in.
#3054, split in multiple smaller PRs, like #3099 would be nice to have.

[guedou]

@polybassa I think that these PR should be added to 2.5.0. @gpotter2 aims to make it the first release that includes typing.

[polybassa]

Alright. Thanks. Than I aim to make everything typed for 2.5

[gpotter2]

Fine by me. I have a few PRs that I like but they can wait for 2.5.