This is useful when the generation of a macOS binary has failed, for
instance.
In addition, we restore checking for the `gh` utility. This is necessary
when running CI locally with `act`.
In addition, we cache pip dependencies on github release and test runs.
In conversations with edX, we learned that the name "edge" had negative
undertones for historical reasons. Thus, we switch to "nightly", which means
pretty much the same thing.
This ensures that any warning generated from compiling the docs is treated as
an error. Also, building the docs is now one of the steps performed in CI.
GitHub Actions now performs the following tasks:
- run tests on every PR
- sync with git.overhang.io on push
- build binary releases on tags
Travis.CI was completely removed from this repo.
