Run tests with actual Python versions

[StrikerRUS]

https://devguide.python.org/#status-of-python-branches

All other versions have reached their EOL.

[mblondel]

Looks OK on my side. @vene may want to take a look too.

[vene]

this implies dropping support for 2.x right?

are the CI failures solved in another PR?

[StrikerRUS]

this implies dropping support for 2.x right?

Right now just stop testing Python 2 and old Python 3 versions.

In further PRs I can help to actually drop Python 2 support and dependency from six (these will be breaking changes).

are the CI failures solved in another PR?

Please refer to #163 (comment). So yes, I'm trying to fix CI failures iteratively with series of self-contained focused on one problem PRs.

[vene]

thanks for clarifying!

i think it's fair to consider untested = unsupported officially, so maybe we should update the readme.

this pr cleans up the CI scripts very nicely, thank you!

[StrikerRUS]

@vene

i think it's fair to consider untested = unsupported officially,

Let me kindly disagree with you, but I totally understand your vision though. I'd better to distinguish untested and unsupported like the following.

untested

"Hey, we don't know whether this works on Python 2 or not, because we don't run tests against it. But you can try and maybe have a luck to get it work!"

unsupported

Python 2 is not supported because (for example) we use f-strings in our codebase which are supported only in 3.6+ version.

[vene]

I see your point, but I think what you are saying does not mean python2 is supported, it just means "code may run on python 2.

Support means a bit more than just "belief it runs without throwing exceptions". Support means also that we can answer bug reports and that if there is some new feature PR in a year or so (e.g. something containing f-strings), we keep py2 support. And the only way to do these things reliably is by running tests on py2.

Leaving open a gap and saying "this might work but you're completely on your own" is not a great idea IMO. Libraries have agonized over this for a long time before py2 was sunset. Now that it has, I think it's ok and better to officially drop support.

[StrikerRUS]

I see your point, but I think what you are saying does not mean python2 is supported, it just means "code may run on python 2.

Exactly!

Now that it has, I think it's ok and better to officially drop support.

Great!

In further PRs I can help to actually drop Python 2 support and dependency from six (these will be breaking changes).
#161 (comment)