Migrate to GitHub Actions.

[jezdez]

Travis CI has a new pricing model which places limits on open source.

• https://blog.travis-ci.com/2020-11-02-travis-ci-new-billing
• https://www.jeffgeerling.com/blog/2020/travis-cis-new-pricing-plan-threw-wrench-my-open-source-works

Many projects are moving to GitHub Actions instead, including Jazzband projects:

• https://github.com/orgs/jazzband/projects/1
• Should we disable travis? help#206

This is based on jazzband/contextlib2#26.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (develop@c59a19f). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             develop     #474   +/-   ##
==========================================
  Coverage           ?   91.54%           
==========================================
  Files              ?       12           
  Lines              ?      852           
  Branches           ?        0           
==========================================
  Hits               ?      780           
  Misses             ?       72           
  Partials           ?        0           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update c59a19f...d76590d. Read the comment docs.

[galuszkak]

@jezdez why we are moving from Travis to Github actions? I'm not sure I understand why this change is coming from.

Travis worked OK here.

[jezdez]

@galuszkak Good question, I should have added a bit more description in the pull request above, lemme add that back. See above!

So in short there are a few reasons: Travis-CI is limiting the number of CI hours for OSS projects massively and requires applying for those credits proactively ahead of time (while also sunsetting travis-ci.org in favor of its commercial travis-ci.com). Given the number of projects in the Jazzband org, it was just a matter of time for this repo to hit throtteling, which would have shown up as much slower processing of jobs (read: waiting days for them to run). Some other Jazzband projects had already been affected negatively in waiting for releases to happen.

Additionally I'm using this chance to clear house a bit, by reducing the maintenance effort needed on my side by reducing the number of CI services. We have or had Circle, Semaphore, Travis, AppVeyor and GitHub Actions. The plan is to have only GitHub Actions going forward.

[galuszkak]

@jezdez thanks, appreciate context you had given. I wasn't aware of it. This make perfect sense.