Start using sage-package to factor out common stuff

[nthiery]

This adds a dependency. But is a step toward reducing the boilerplate in our packages by factoring it out in a single package. This also makes it easier to enhance that boilerplate to add new features (e.g. improvements to the Sphinx theme, which could include live doc support).

What do you think?

[mmasdeu]

I hadn't realized that this existed. I made another package (called sagemath) in PyPI that has a similar purpose. In my branch this dependency already exists. Maybe one can merge both packages into a single one (and remove the other to avoid confusion). What are your thoughts? @nthiery @williamstein @mkoeppe @videlec ?

[embray]

@mmasdeu If there's a "sagemath" on PyPI that should be for the sagemath package itself, which at least one day will be on PyPI...

[williamstein]

This sagemath PyPi package will be for the sagemath package itself, eventually. Right now it is a placeholder package, which when installed either works (since it’s installed into sage) or says something like “you must install sagemath from sagemath.org...”

[seblabbe]

I am currently at Sage Days 117. There was a demo earlier this week on how to share code and create a package where we used sage_sample. I am now taking a look at all the PR that have been here for years now...

No discussion has never been made about who should merge PRs.

The current PR has conflicts. I let the author or someone else fix them.