Bug#896218: python-brial: brial fails to import

[Helmut Grohne]

On Sat, Apr 21, 2018 at 11:11:52AM +0200, Tobias Hansen wrote:
> thanks for the bug report. We are aware that brial has a circular dependency with sagemath. src:sagemath build-depends on src:brial and python-brial should depend on sagemath. We didn't add this dependency in order not to manifest the circular dependency in the package relationships. We brought this up with upstream once (can't find it now) but they didn't care. For that reason I don't know if there is anything to be done at the moment.

Avoiding the circular dependency is a good thing. Let me suggest some
ways to improve the situation anyway:

 * python-brial could at least Recommends: sagemath. Doing so wouldn't
   manifest in Build-Depend and thus does not constitute a cycle.
 * If sagemath uses python-brial for testing only (I cannot tell), then
   you can annotate the build dependency with <!nocheck> introducing a
   better way to break the cycle. If that works, I think having the
   cycle in the normal case is a better trade-off.
 * Sometimes it is feasible to move build dependencies to
   Build-Depends-Indep. That can also be used as a cycle breaker.
 * Since brial does not Build-Depends: sagemath, is there actually a
   cycle? Or can you simply go and add the dependency.

Helmut