Downgrade rubiks to optional

[isuruf]

See discussion in ​https://groups.google.com/forum/?utm_medium=email&utm_source=footer#!msg/sage-devel/lc-HqYCFrDw/r4TlV6qCBAAJ

[chapoton]

here is first tentative

---

New commits:

​0da2479

trac 28022 downgrade rubiks to optional

[dimpase]

this also needs an update of http://wrongway.org/?rubiksource in rubiks.py, as it's not working any more (domain is up for sale).

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​9a9087a

trac 28022 change dead url to web archive version

[chapoton]

done

[embray]

+1 Would it make sense to use sage.features for this?

[jdemeyer]

If we're not changing the package, there is no need to edit build/pkgs/rubiks/package-version.txt

[git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

​fbc54a1

trac 28022 downgrade rubiks to optional

[chapoton]

version bump was undone, and then the branch squashed

[dimpase]

OK, don't forget the author's name.

[chapoton]

thx

[dimpase]

We forgot src/sage/groups/perm_gps/cubegroup.py, where rubiks is used unconditionally.

[git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

​5f27079	trac 28022 downgrade rubiks to optional
​1ecfad6	trac 28022 adding more optional rubiks tags

[chapoton]

indeed. Here is a fix.

[dimpase]

this seems to be a wrong (always succeeding) test for the presense of rubiks package:

        try:
            import sage.interfaces.rubik  # here to avoid circular referencing
        except ImportError:
            algorithm = 'gap'

indeed, the interface is always there, whether or not rubiks is installed.

[chapoton]

ok.. Then I have no idea what to do. If you know how to fix that, please do..

[dimpase]

How about simply calling is_package_installed('rubiks') ?

sage: is_package_installed('rubiks')
False

[gh-timokau]

Note that is_package_installed is supposed to be deprecated: ​https://trac.sagemath.org/ticket/20382, mostly (I think) because it is a pain for packagers.

[dimpase]

Features entails creating sage/features/rubiks.py with some runtime tests... looks a bit insane, but OK...

[jhpalmieri]

According to the file manifest, the rubiks package only installs six binaries, and it shouldn't be too bad to check that they exist and work, for the Features test. You could model it on sage/features/graphviz.py, for example.

[embray]

+1 to adding it to sage.features. This is what I suggested in the first place :)

[chapoton]

I will not be the one that does that.

[embray]

Ticket retargeted after milestone closed

[mkoeppe]

Batch modifying tickets that will likely not be ready for 9.1, based on a review of the ticket title, branch/review status, and last modification date.

[git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

​a8ea381

trac 28022: rebased Frédéric Chapoton's branch, added Features support

[jhpalmieri]

I rebased Frédéric's work, and I added a file features/rubiks.py. Please test with and without installing the rubiks package.

[mkoeppe]

This works well.