Created attachment 639682 [details]
This will likely also affect 'regular' scipy.
Fixed upstream in https://github.com/scipy/scipy/pull/11842 so for -python2 this patch might need to be backported or maybe we could just set FFLAGS in the ebuild.
I was able to build scipy-python2 like this:
FFLAGS=-fallow-argument-mismatch emerge -va1 scipy-python2