Testing issue: py-matplotlib fails to execute build time tests

[tpadioleau]

Steps to reproduce the failure(s) or link(s) to test output(s)

$ spack install --test=root py-matplotlib

Error message

Error message

[x] 2iwlblt py-matplotlib@3.11.0 failed: /tmp/tpadiole/spack-stage/spack-stage-py-matplotlib-3.11.0-2iwlbltojhohdgww5extlnjbvg7vglhb-myq0x0w1.log (29s)
-- lines 696 to 715 --
  Building wheels for collected packages: matplotlib
    Destination directory: /tmp/pip-ephem-wheel-cache-lv3kxq4p/wheels/08/89/7d/2fbebbc9b28e90506d2a25fb825e82c7ddd39c77279ae3f535/tmpixgl1axg
    Building wheel for matplotlib (pyproject.toml): started
    Running command Building wheel for matplotlib (pyproject.toml)
    Building wheel for matplotlib (pyproject.toml): finished with status 'done'
    Created wheel for matplotlib: filename=matplotlib-3.11.0-cp314-cp314-linux_x86_64.whl size=8397922 sha256=2f91a63377862008949a8f698ce9f1eb53b19d057d3668fa6b37ea94d9c67d0b
    Stored in directory: /tmp/pip-ephem-wheel-cache-lv3kxq4p/wheels/08/89/7d/2fbebbc9b28e90506d2a25fb825e82c7ddd39c77279ae3f535
  Successfully built matplotlib
  Installing collected packages: matplotlib
  
  Successfully installed matplotlib-3.11.0
  Removed build tracker: '/tmp/pip-build-tracker-fez8vv62'
  ==> [2026-08-05-13:22:14.928842] Installing lib/matplotlib/tests/baseline_images to /local/home/tpadiole/spack-1.2.2/opt/spack/linux-x86_64/py-matplotlib-3.11.0-2iwlbltojhohdgww5extlnjbvg7vglhb/lib/python3.14/site-packages/matplotlib/tests/baseline_images
  ==> [2026-08-05-13:22:15.169521] Installing lib/mpl_toolkits/axes_grid1/tests/baseline_images to /local/home/tpadiole/spack-1.2.2/opt/spack/linux-x86_64/py-matplotlib-3.11.0-2iwlbltojhohdgww5extlnjbvg7vglhb/lib/python3.14/site-packages/mpl_toolkits/axes_grid1/tests/baseline_images
  ==> [2026-08-05-13:22:15.171283] Installing lib/mpl_toolkits/axisartist/tests/baseline_images to /local/home/tpadiole/spack-1.2.2/opt/spack/linux-x86_64/py-matplotlib-3.11.0-2iwlbltojhohdgww5extlnjbvg7vglhb/lib/python3.14/site-packages/mpl_toolkits/axisartist/tests/baseline_images
  ==> [2026-08-05-13:22:15.184152] Installing lib/mpl_toolkits/mplot3d/tests/baseline_images to /local/home/tpadiole/spack-1.2.2/opt/spack/linux-x86_64/py-matplotlib-3.11.0-2iwlbltojhohdgww5extlnjbvg7vglhb/lib/python3.14/site-packages/mpl_toolkits/mplot3d/tests/baseline_images
  ==> [2026-08-05-13:22:15.192476] /local/home/tpadiole/spack-1.2.2/opt/spack/linux-x86_64/python-venv-1.0-yswa3xmhktj7y2xv5l4rgl6qhwncdl4f/bin/python3 -m pytest --pyargs matplotlib.tests
  /local/home/tpadiole/spack-1.2.2/opt/spack/linux-x86_64/python-venv-1.0-yswa3xmhktj7y2xv5l4rgl6qhwncdl4f/bin/python3: No module named pytest
  Command exited with status 1:
      /local/home/tpadiole/spack-1.2.2/opt/spack/linux-x86_64/python-venv-1.0-yswa3xmhktj7y2xv5l4rgl6qhwncdl4f/bin/python3 -m pytest --pyargs matplotlib.tests
==> Error: The following packages failed to install:
py-matplotlib@3.11.0/2iwlbltojhohdgww5extlnjbvg7vglhb: /tmp/tpadiole/spack-stage/spack-stage-py-matplotlib-3.11.0-2iwlbltojhohdgww5extlnjbvg7vglhb-myq0x0w1.log

Information on your system or the test runner

• Spack: 1.2.2
• Builtin repo: d4f7c71
• Python: 3.14.4
• Platform: linux-ubuntu26.04-icelake

Additional information

spack-stage-py-matplotlib-3.11.0-2iwlbltojhohdgww5extlnjbvg7vglhb-myq0x0w1.log

This follows the discussion from #5589, @adamjstewart @rgommers

General information

• I have reported the version of Spack/Python/Platform/Runner
• I have run spack maintainers <name-of-the-package> and @mentioned any maintainers
• I have uploaded any available logs
• I have searched the issues of this repo and believe this is not a duplicate