Repair self-containedness of the wrapped spkg-install scripts for Python packages

[Matthias Köppe]

Follow-up from #29500.

When an spkg fails to install, Sage advises:

[pynormaliz-2.12] If you want to try to fix the problem yourself, *don't* just cd to
[pynormaliz-2.12] /Users/mkoeppe/s/sage/sage-rebasing/worktree-algebraic-2018-spring/local/var/tmp/sage/build/pynormaliz-2.12 and type 'make' or whatever is appropriate.
[pynormaliz-2.12] Instead, the following commands setup all environment variables
[pynormaliz-2.12] correctly and load a subshell for you to debug the error:
[pynormaliz-2.12]   (cd '/Users/mkoeppe/s/sage/sage-rebasing/worktree-algebraic-2018-spring/local/var/tmp/sage/build/pynormaliz-2.12' && '/Users/mkoeppe/s/sage/sage-rebasing/worktree-algebraic-2018-spring/sage' --buildsh)

In the shell set up with this command, one used to be able to just type ./spkg-install to re-run the (wrapped) installation script.

#29500 inadvertently broke this for Python packages because sdh_pip_install now depends on an additional environment variable that is set in sage-spkg: SAGE_SPKG_WHEELS. This leads to the following error:

Successfully installed PyNormaliz-2.12
Removed build tracker: '/private/var/folders/38/wnh4gf1552g_crsjnv2vmmww0000gp/T/pip-req-tracker-kweqslvi'
mkdir: : No such file or directory
********************************************************************************
Error storing dist/PyNormaliz-2.12-cp37-cp37m-macosx_10_9_x86_64.whl
********************************************************************************

We fix it by setting this variable in the wrapped spkg-install scripts.

Blocker for 9.2 because this defect interferes with the debugging of spkg scripts; and because the priority "critical" seems to be ignored by the release management scripts.

[Matthias Köppe]

New commits:

​3cd351c

build/bin/sage-spkg: Set SAGE_SPKG_WHEELS in wrapped scripts

[Matthias Köppe]

Can we get this into Sage 9.2 please?

[John Palmieri]

The change seems innocuous, but I'm not sure how to test it.

[Matthias Köppe]

Interrupt an installation of a Python package with ^C (or provoke an error otherwise), then restart the installation as described in the ticket

[John Palmieri]

Okay, it works for me. I'm not sure why you wouldn't just try make PKG, but I guess for some debugging people might want to run spkg-install directly. It doesn't strike me as critical, but whatever.

[Matthias Köppe]

Thanks!

[Matthias Köppe]

Replying to jhpalmieri:

I'm not sure why you wouldn't just try make PKG

This unpacks the tarball another time. For debugging, it is useful to make changes to the unpackaged source tree.

[Volker Braun]

Better development experience can't be a blocker

[gh-kliem]

I don't think this is developers only. I hope that optional packages are also used by non-developers.

Failure to install packages is unfortunately still common and could happen to anyone compiling sage from source. The standard debugging instruction as in the description of this ticket should work and I think such a tiny fix should go into the next master branch.