Bug#1043048: openblas: gives wrong results on mips64el, ignores test failures

[Rebecca N. Palmer]

Package: libopenblas0-pthread
Version: 0.3.23+ds-2
Control: affects -1 src:statsmodels
Severity: serious
Justification: the default BLAS should NOT silently give wrong answers
(i.e. if there's no easy way to actually fix this, please switch the 
default on mips64el back to atlas, and consider removing this package 
from mips64el)

statsmodels recently (between 0.14.0+dfsg-1 and -2) started to FTBFS on 
mips64el with multiple wrong test results.  The most obviously relevant 
change between those is that the installed BLAS changed from atlas to 
openblas.

openblas' own tests on mips64el ( 
https://buildd.debian.org/status/fetch.php?pkg=openblas&arch=mips64el&ver=0.3.23%2Bds-2&stamp=1686760279&raw=0 
) have 64 instances of "FATAL ERROR - COMPUTED RESULT IS LESS THAN HALF 
ACCURATE".  (I don't know why this isn't failing the build, which is 
possibly a bug in itself.)

openblas upstream are not _obviously_ aware of this.  Given the 
existence of .github/workflows/mips64.yml, this suggests it _may_ be 
nontrivial to reproduce in qemu.