Add Python 3.8 & 3.9 as supported versions

[kaxil]

Since Py 3.8 is supported, we should update the "classifiers", as it is shown on PyPI and gives wrong impressions that Py 3.8 is not supported.

This PR also adds Py 3.9 and adds them to CI

[coveralls]

Coverage remained the same at 90.239% when pulling 881d834 on kaxil:patch-1 into fb3ec4e on requests:master.

[hugovk]

This will fix #443.

How about adding Python 3.9 as well, and testing both 3.8 and 3.9 on the CI too?

[kaxil]

@hugovk Done

[hugovk]

Please could someone from this organisation enable/transfer Travis CI from .org to .com?

[jsadn]

@jtroussard any chance you can get this merged with the impending python EOL

[hugovk]

Which impending EOL?

Python 3.10 is due out today, we could also add 3.10 too :) (Would need to be 3.10-dev on Travis CI until they add the 3.10.0 release in a few weeks' time.)

https://twitter.com/pyblogsal/status/1442890650303664131

[kaxil]

Which impending EOL?

Python 3.10 is due out today, we could also add 3.10 too :) (Would need to be 3.10-dev on Travis CI until they add the 3.10.0 release in a few weeks' time.)

https://twitter.com/pyblogsal/status/1442890650303664131

tbh that can be done in a follow-up PR too, we shouldn't need to wait for it.

[jsadn]

Which impending EOL?

I was referring 3.6 in December 2021.
3.7 is on the supported list I suppose, but I'd love to use this lib with confidence for py 3.8.

[jtroussard]

@JonathanHuot would you be able to take a peek on these conflicts? I believe this PR should be an easy review/merge. Correct me if I am wrong but we have agreed to move away from travisCI? If so we can remove that file from this PR.

[kaxil]

@JonathanHuot would you be able to take a peek on these conflicts? I believe this PR should be an easy review/merge. Correct me if I am wrong but we have agreed to move away from travisCI? If so we can remove that file from this PR.

I have rebased and fixed conflicts, hopefully this time around this will be merged :)

[jtroussard]

lgtm