Change:
msgpack ]; <ins> preBuild = if (stdenv.hostPlatform.isx86 && !stdenv.hostPlatform.avx2Support) then '' export DISABLE_NUMCODECS_AVX2= '' else null; </ins> nativeCheckInputs = [ pytestCheckHook ];

Discussion:
Right now it tests, probably because of getting scheduled on a bit older machine than usually. Log may get overwritten if restarted on Hydra, so here's the relevant part: <details<prerunning install tests ============================= test session starts ============================== platform linux -- Python 3.10.1, pytest-6.2.5, py-1.11.0, pluggy-1.0.0 rootdir: /build/zarr-2.10.3, configfile: collecting . Fatal Python error: Illegal instruction Current thread 0x00007ffff77d8440 (most recent call first): File "<frozen importlib.bootstrap", line 241 in callwithframesremoved File "<frozen importlib.bootstrapexternal", line 1184 in execmodule File "<frozen importlib.bootstrap", line 688 in loadunlocked File "<frozen importlib.bootstrap", line 1006 in findandloadunlocked File "<frozen importlib.bootstrap", line 1027 in findandload File "/nix/store/icv204idxppknvjbpwrfqqymxbdhfqkv-python3.10-numcodecs-0.9.1/lib/python3.10/site-", line 4 in <moduleFile "<frozen importlib.bootstrap", line 241 in callwithframesremoved File "<frozen importlib.bootstrapexternal", line 883 in execmodule File "<frozen importlib.bootstrap", line 688 in loadunlocked File "<frozen importlib.bootstrap", line 1006 in findandloadunlocked File "<frozen importlib.bootstrap", line 1027 in findandload File "/nix/store/icv204idxppknvjbpwrfqqymxbdhfqkv-python3.10-numcodecs-0.9.1/lib/python3.10/site-", line 100 in <moduleFile "<frozen importlib.bootstrap", line 241 in callwithframesremoved File "<frozen importlib.bootstrapexternal", line 883 in execmodule File "<frozen importlib.bootstrap", line 688 in loadunlocked File "<frozen importlib.bootstrap", line 1006 in findandloadunlocked File "<frozen importlib.bootstrap", line 1027 in findandload File "/build/zarr-", line 2 in <moduleFile "<frozen importlib.bootstrap",

line 241 in callwithframesremoved File "<frozen importlib.bootstrapexternal", line 883 in execmodule File "<frozen importlib.bootstrap", line 688 in loadunlocked File "<frozen importlib.bootstrap", line 1006 in findandloadunlocked File "<frozen importlib.bootstrap", line 1027 in findandload File "/build/zarr-", line 2 in <moduleFile "<frozen importlib.bootstrap", line 241 in callwithframesremoved File "<frozen importlib.bootstrapexternal", line 883 in execmodule File "<frozen importlib.bootstrap", line 688 in loadunlocked File "<frozen importlib.bootstrap", line 1006 in findandloadunlocked File "<frozen importlib.bootstrap", line 1027 in findandload File "<frozen importlib.bootstrap", line 1050 in gcdimport File "<frozen importlib.bootstrap", line 241 in callwithframesremoved File "<frozen importlib.bootstrap", line 992 in findandloadunlocked File "<frozen importlib.bootstrap", line 1027 in findandload File "<frozen importlib.bootstrap", line 1050 in gcdimport File "<frozen importlib.bootstrap", line 241 in callwithframesremoved File "<frozen importlib.bootstrap", line 992 in findandloadunlocked File "<frozen importlib.bootstrap", line 1027 in findandload File "<frozen importlib.bootstrap", line 1050 in gcdimport File "/nix/store/fi0f5rz33byvsqlzs5hcc6l25scdlg42-python3-", line 126 in importmodule File "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-6.2.5/lib/python3.10/site-", line 524 in importpath File "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-6.2.5/lib/python3.10/site-", line 570 in importconftest File "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-6.

2.5/lib/python3.10/site-", line 536 in getconftestmodules File "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-6.2.5/lib/python3.10/site-", line 519 in gethookproxy File "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-6.2.5/lib/python3.10/site-", line 551 in collectfile File "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-6.2.5/lib/python3.10/site-", line 702 in collect File "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-6.2.5/lib/python3.10/site-", line 341 in <lambdaFile "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-6.2.5/lib/python3.10/site-", line 311 in fromcall File "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-6.2.5/lib/python3.10/site-", line 341 in pytestmakecollectreport File "/nix/store/94g90xjsfq8pk8wh67v388nw3m07bp2f-python3.10-pluggy-1.0.0/lib/python3.10/site-", line 39 in multicall File "/nix/store/94g90xjsfq8pk8wh67v388nw3m07bp2f-python3.10-pluggy-1.0.0/lib/python3.10/site-", line 80 in hookexec File "/nix/store/94g90xjsfq8pk8wh67v388nw3m07bp2f-python3.10-pluggy-1.0.0/lib/python3.10/site-",

line 265 in call File "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-6.2.5/lib/python3.10/site-", line 458 in collectonenode File "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-6.2.5/lib/python3.10/site-", line 620 in performcollect File "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-6.2.5/lib/python3.10/site-", line 333 in pytestcollection File "/nix/store/94g90xjsfq8pk8wh67v388nw3m07bp2f-python3.10-pluggy-1.0.0/lib/python3.10/site-", line 39 in multicall File "/nix/store/94g90xjsfq8pk8wh67v388nw3m07bp2f-python3.10-pluggy-1.0.0/lib/python3.10/site-", line 80 in hookexec File "/nix/store/94g90xjsfq8pk8wh67v388nw3m07bp2f-python3.10-pluggy-1.0.0/lib/python3.10/site-", line 265 in call File "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-6.2.5/lib/python3.10/site-", line 322 in main File "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-6.2.5/lib/python3.10/site-", line 269 in wrapsession File "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-6.2.5/lib/python3.10/site-", line 316 in pytestcmdlinemain File "/nix/store/94g90xjsfq8pk8wh67v388nw3m07bp2f-python3.

10-pluggy-1.0.0/lib/python3.10/site-", line 39 in multicall File "/nix/store/94g90xjsfq8pk8wh67v388nw3m07bp2f-python3.10-pluggy-1.0.0/lib/python3.10/site-", line 80 in hookexec File "/nix/store/94g90xjsfq8pk8wh67v388nw3m07bp2f-python3.10-pluggy-1.0.0/lib/python3.10/site-", line 265 in call File "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-6.2.5/lib/python3.10/site-", line 162 in main File "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-6.2.5/lib/python3.10/site-", line 185 in consolemain File "/nix/store/kq60a6md5pm6sgyzlvqxhqxll7g6hdrj-python3.10-pytest-", line 9 in <moduleExtension modules: , , , , , , , , , , , , , , numcodecs.compatext, , , numcodecs.lz4, numcodecs.shuffle (total: 19) /nix/store/vhdfrizjvb4p58wkidl8hmn5gnp9zbxv-stdenv-linux/setup: line 1352: 121 Illegal instruction (core dumped) pytest builder for '/nix/store/2pr9j3b2fzkbfmjglbsyr8anxmc2h0v6-python3.10-zarr-' failed with exit code 132 </pre</detailsThis looks somewhat similar to but the CPU in question here is not that old (Ivy Bridge, i.e. arch < 10 years):
add a tensorflow for slow cpus without avx2/sse42/fma? require the cpu flags avx2/sse42/fma in mkDerivation meta? (mxnet comment moved to )
Running into this as well. Using an Intel Xeon .

with flags: I don't know how to better determine what illegal instruction was executed. I'm not sure is the responsible package. I'm leaning towards . That said, python packaging is not something I'm familiar with so ???