support Python 3.10

[orbeckst]

Enable testing for Python 3.10 (and fix anything that needs fixing).

[IAlibay]

Given the recent issues with six in the core library (highlighting this library as one of the core dependencies still requiring it), is it worth revisiting its use?

Looking at their issue tracker, I think there's a fix for py3.10 for six but it's probably not coming for some time.

[orbeckst]

We can drop 2.7 and six if it creates issues.

…

Am 12/29/21 um 18:36 schrieb Irfan Alibay ***@***.***>:  Given the recent issues with six in the core library (highlighting this library as one of the core dependencies still requiring it), is it worth revisiting its use? Looking at their issue tracker, I think there's a fix for py3.10 for six but it's probably not coming for some time. — Reply to this email directly, view it on GitHub, or unsubscribe. Triage notifications on the go with GitHub Mobile for iOS or Android. You are receiving this because you authored the thread.

[orbeckst]

Is six not working with 3.10?

if that’s the case then my comment in #102 to drop legacy for 1.0 is moot — we do want to support 3.10 asap.

[IAlibay]

I've not had time to really dig into it - there's a bunch of warnings that could be problematic, but it hasn't affected the outcome of the MDA testsuite, so whatever it's affecting isn't impacting most things probably?

[IAlibay]

I think six is now working again with py3.10 (see v1.16.0 in https://github.com/benjaminp/six/blob/master/CHANGES).

As far as I can tell the six code isn't regularly tested with py3.10, but we can see what happens?