Drop Python 2

[lafrech]

Let's wait on #420 to be merged first to avoid a painful rebase.

• Drop Python 2
• Make arguments keyword-only where sensible

Do we also want to drop Python 3.5 ? This can be done in a later major release.

[sloria]

Wrote up a checklist recently for this: https://gist.github.com/sloria/b4a5fc2281f86a5733af198d609c5ab3

[sirosen]

I wanted to chime in with my $0.02: I wouldn't drop py3.5 support yet because it's the py3 version shipped on several distro versions, notably Ubuntu 16.04.
Since so many people are using Ubuntu as their first distro, and there's the WSL stuff on Windows, there's some reason to give the Ubuntu lifecycle "priority" when looking at the landscape of distros.

By way of example, if someone is using webargs but they're having trouble upgrading from Ubuntu 16.04 infrastructure to Ubuntu 18.04, then they wouldn't be able to move to the new webargs without either (A) fixing their platform version issues or (B) installing another python version alongside the system python. (Yes, they should fix their problems, but my experience is that by the time you're even talking about being stuck on an old platform version, you're in trouble.)

The same argument doesn't apply to forcing the py2 -> py3 transition -- I'm 👍 on dropping py2.

[lafrech]

Yeah, no pressure to remove py35 soon. Can be done later.

[sloria]

Sounds good. I'm fine keeping support for 3.5 for now.

[lafrech]

Summoning @hugovk again.

Would you be willing to tackle this?

Just asking. I don't know if you even use webargs.

[hugovk]

Happy to help with Python 3 migration!

Please see PR #454 for the first checkbox item: " Drop Python 2".

The second checkbox "Make arguments keyword-only where sensible" can follow in another PR.

[sirosen]

With #472 merged, we can call this done!

I just did a check on the repo looking for anything python2-related I could find and it came up blank.