[bug#44590] [WIP PATCH CORE-UPDATES] build/python: Check for cythonized files.

[Simon South <simon@simonsouth.net>]

Efraim,

I'm seeing an issue I think is related to this change. Trying to build
glib in core-updates today fails for me with "Unbound variable: warning"
in python-build-system.scm:

    starting phase `ensure-no-cythonized-files'
    Backtrace:
               9 (primitive-load "/gnu/store/ycv4j8dqk44g6d72m2ykvlwb9wc?")
    In ice-9/eval.scm:
       191:35  8 (_ _)
    In guix/build/gnu-build-system.scm:
        886:2  7 (gnu-build #:source _ #:outputs _ #:inputs _ #:phases . #)
    In ice-9/boot-9.scm:
      1736:10  6 (with-exception-handler _ _ #:unwind? _ # _)
    In srfi/srfi-1.scm:
        634:9  5 (for-each #<procedure 7ffff4f662e0 at guix/build/gnu-b?> ?)
    In guix/build/gnu-build-system.scm:
       895:33  4 (_ _)
    In guix/build/python-build-system.scm:
        272:2  3 (ensure-no-cythonized-files . _)
    In srfi/srfi-1.scm:
        634:9  2 (for-each #<procedure 7ffff5ad3978 at guix/build/pytho?> ?)
    In guix/build/python-build-system.scm:
       277:10  1 (_ _)
    In ice-9/boot-9.scm:
      1669:16  0 (raise-exception _ #:continuable? _)

    ice-9/boot-9.scm:1669:16: In procedure raise-exception:
    Unbound variable: warning
    builder for `/gnu/store/cgmgrddwjvryxmj4nn3naiwy42yi3wzn-meson-for-build-0.55.1.drv' failed with exit code 1
    build of /gnu/store/cgmgrddwjvryxmj4nn3naiwy42yi3wzn-meson-for-build-0.55.1.drv failed
    View build log at '/var/log/guix/drvs/cg/mgrddwjvryxmj4nn3naiwy42yi3wzn-meson-for-build-0.55.1.drv.bz2'.
    cannot build derivation `/gnu/store/a00wr5wj4cd0b98ixxynyxgbw2nyv8kg-glib-2.62.6.drv': 1 dependencies couldn't be built
    guix build: error: build of `/gnu/store/a00wr5wj4cd0b98ixxynyxgbw2nyv8kg-glib-2.62.6.drv' failed

And in fact building python-build-system.scm shows

    [100%] GUILEC   guix/build/python-build-system.go
    WARNING: (guix build python-build-system): imported module (guix build utils) overrides core binding `delete'
    guix/build/python-build-system.scm:277:10: warning: possibly unbound variable `warning'
    guix/build/python-build-system.scm:277:19: warning: possibly unbound variable `G_'

Adding use-module directives for (guix diagnostics) and (guix i18n) to
the module doesn't seem to fix the problem, presumably (if I understand
correctly) because these modules are not then also imported on the build
side of things.

Are you aware of this issue?

-- 
Simon South
simon@simonsouth.net