build.yml: Incremental build&test fails with pytest/matplotlib error

[mkoeppe]

seen in https://github.com/sagemath/sage/actions/runs/5349116550/jobs/9699980883?pr=35808

Using --optional=debian,pip,sage,sage_spkg
Features to be detected: 4ti2,benzene,bliss,buckygen,conway_polynomials,csdp,cvxopt,cvxopt,database_cremona_ellcurve,database_cremona_mini_ellcurve,database_cubic_hecke,database_jones_numfield,database_knotinfo,dvipng,fpylll,gfan,graphviz,imagemagick,ipython,jupymake,kenzo,latte_int,lrcalc_python,lrslib,mcqd,meataxe,mpmath,msolve,nauty,networkx,numpy,palp,pandoc,pdf2svg,pdftocairo,pexpect,phitigra,pillow,plantri,polytopes_db,polytopes_db_4d,pplpy,primecountpy,ptyprocess,pynormaliz,pyparsing,python_igraph,requests,rubiks,sage.combinat,sage.geometry.polyhedron,sage.graphs,sage.groups,sage.libs.flint,sage.libs.gap,sage.libs.ntl,sage.libs.pari,sage.libs.singular,sage.misc.cython,sage.modular,sage.modules,sage.plot,sage.rings.finite_rings,sage.rings.function_field,sage.rings.number_field,sage.rings.padics,sage.rings.polynomial.pbori,sage.rings.real_double,sage.rings.real_mpfr,sage.schemes,sage.symbolic,sage_numerical_backends_coin,sagemath_doc_html,scipy,singular,sphinx,sympy,tdlib
Doctesting files changed since last git commit
No files to doctest
Features detected for doctesting: 
Running pytest on [] with options []
============================= test session starts ==============================
platform linux -- Python 3.8.10, pytest-7.3.2, pluggy-1.0.0
rootdir: /sage
plugins: mock-3.11.1
collected 0 items / 1 error

==================================== ERRORS ====================================
________________________ ERROR collecting test session _________________________
/usr/lib/python3.8/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
<frozen importlib._bootstrap>:1014: in _gcd_import
    ???
<frozen importlib._bootstrap>:991: in _find_and_load
    ???
<frozen importlib._bootstrap>:961: in _find_and_load_unlocked
    ???
<frozen importlib._bootstrap>:219: in _call_with_frames_removed
    ???
<frozen importlib._bootstrap>:1014: in _gcd_import
    ???
<frozen importlib._bootstrap>:991: in _find_and_load
    ???
<frozen importlib._bootstrap>:975: in _find_and_load_unlocked
    ???
<frozen importlib._bootstrap>:671: in _load_unlocked
    ???
<frozen importlib._bootstrap_external>:848: in exec_module
    ???
<frozen importlib._bootstrap>:219: in _call_with_frames_removed
    ???
local/var/lib/sage/venv-python3.8/lib/python3.8/site-packages/matplotlib/tests/__init__.py:6: in <module>
    raise IOError(
E   OSError: The baseline image directory does not exist. This is most likely because the test data is not installed. You may need to install matplotlib from source to get the test data.
=========================== short test summary info ============================
ERROR  - OSError: The baseline image directory does not exist. This is most likely because the test data is not installed. You may need to install matplotlib from source to get the test data.
!!!!!!!!!!!!!!!!!!!! Interrupted: 1 error during collection !!!!!!!!!!!!!!!!!!!!
============================== 1 error in 11.47s ===============================
Error: Process completed with exit code 2.

[kwankyu]

Would this be fixed by #35865? Or is this still out of clue?

[mkoeppe]

Haven't seen this in a while, closing