Bug#940679: pandas: random test crashes

[Rebecca N. Palmer]

The ppc64 failure was this bug, specifically the
pandas/tests/indexes/interval/test_astype.py::TestDatetimelikeSubtype::test_astype_category[index3] 
version.  It was retried successfully.  (The hppa failure is something 
else.)

The "Build environment" section of the build log (i.e. the versions of 
all installed packages, both build-essential and explicit dependencies) 
is identical between the failed and successful attempts.

pandas isn't fully reproducible, but the -lib parts (i.e. where one can 
get a segfault as opposed to an exception) are 
(https://tests.reproducible-builds.org/debian/rb-pkg/unstable/armhf/diffoscope-results/pandas.html), 
so this suggests the randomness is per test run not per build.

And hence that it only happens when running more than just these tests 
(given that it didn't happen in far more attempts of that).

debci has one failure that _might_ be this (it's old enough that the log 
has been deleted) out of ~140 attempts, which suggests the bug is new. 
(Or newly exposed: maybe by locales-all, added as a build/test 
dependency in -5?)