Bug#1034443: python3-brial: uninstallable on arcitectures where sagemath is unavailable, breaks building of singular

[Peter Green]

Package: python3-brial
Version: 1.2.11-2
Severity: serious
X-debbugs-cc: singular at packages.debian.org

python3-brial recently added a dependency on python3-sage, however python3-sage
is only available on amd64, arm64, i386 and riscv64.

This also means that the build-depends of singular on those architectures are
unsatisfied.

Strangely, when I look at the singular build log the only mentions of brial
I see are in the Debian packaging steps, I don't see any mentions of it from
the upstream build system. Grepping for brial in the polybori source doesn't
reveal anything outside the debian dir either. I maintain a downstream
distribution and, after removing the build-dependency, was able to build
singular there without having any brial related packages installed.

So assuming the dependency on python3-sage is real and unavoidable what I
think needs to happen to get things back in a consistent state is.

* The architecture list of python3-brial needs to be limited to architectures
   where python3-sage is available.
* The build-dependency of singular on python3-brial needs to be either
   removed or limited to architectures where python3-sage is available
* Removal of the old python3-brial packages needs to be requested.