Upgrade

[eyllanesc]

• [x] Migrate from travis to Github Workflows.
• [x] Add dependabot.
• [x] Upgrade requirements-dev.txt.
• [x] Upgrade to python 3.6, 3.7, 3.8, 3.9 and 3.10.
• [x] Upgrade nose to nose2.

[twolfson]

Thanks for the PR =) Unfortunately, I don't want a lot of these changes =/

• A lot of my repos are on Travis CI, so switching to GitHub is a mass migration that I don't have bandwidth to start any time soon
• We receive dependabot security alerts, but this repo also has few dependencies =/
• Glad to receive the other updates (e.g. expanding CI Python testing, nose2) but would appreciate explanations behind them since nothing seems broken and no bug reports coming in

[eyllanesc]

I understand your points. I offer you the following alternative:

Do not remove travis but add GA. GA could be used for recent versions of python and others OS which doesn't seem to be covered in travis. The dependabot thing could be optional, I don't see a great advantage but not a big problem either, I will only create PR of updates. What do you think?

[twolfson]

Eh, we're not doing anything sophisticated/new language feature dependent, so testing early Python 3.x prob covers us quite well still. I think Travis CI is good enough for now

[eyllanesc]

My initial proposal was caused by seeing travis.ci badge in the README pointing out that there was a problem. Then I noticed that you were testing with versions of python that are no longer supported, so I thought that perhaps with new versions of python something could have been broken but it is not, but perhaps in the future it could happen. Anyway the changes depend on you. Goodbye, thanks for your time.

[twolfson]

Ah, I see. We just shifted from Travis CI org to com so it's likely related to that issue. Thanks for the heads up =)