[ci skip]

The code might still work, but it is no longer tested.
You can use releases in the 1.10 series on the older versions.

Theoretically our tests might work, but there is definitely other code that would have test failures,
so you should not use it on 5.2.
And no easy way to already test on 6.0.  But we have buildout.coredev and Jenkins.

I thought I did that already, but this was only in tox.ini.  It was still in the travis config.

Seems better, as the other envs at most use 3.8.
And on Travis the docs env fails, with no output.  Maybe this helps.

See also the closed PR #455 where I try a few Python versions and add some comments.