BUG: "Spinx parallel build error" when running `python make.py html`

[tpaxman]

Pandas version checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

after setting up the pandas-dev environment and building pandas as described in the instructions, and changing to doc/ directory run these commands:

python make.py clean
python make.py html

Issue Description

Getting this error:

Sphinx parallel build error:
RuntimeError: Non Expected warning in `/home/tpaxman/code/pandas-tpaxman/doc/source/getting_started/intro_tutorials/04_plotting.rst` line 70

I believe there was a similar error occurring previously that was fixed with #53726 but seems that the error is happening again.

Expected Behavior

No error

Installed Versions

INSTALLED VERSIONS

commit : bd9a671
python : 3.10.11.final.0
python-bits : 64
OS : Linux
OS-release : 5.15.90.1-microsoft-standard-WSL2
Version : #1 SMP Fri Jan 27 02:56:13 UTC 2023
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : C.UTF-8
LOCALE : en_US.UTF-8

pandas : 2.1.0.dev0+1018.gbd9a67131a
numpy : 1.24.3
pytz : 2023.3
dateutil : 2.8.2
setuptools : 67.7.2
pip : 23.1.2
Cython : 0.29.33
pytest : 7.3.2
hypothesis : 6.79.1
sphinx : 6.2.1
blosc : None
feather : None
xlsxwriter : 3.1.2
lxml.etree : 4.9.2
html5lib : 1.1
pymysql : 1.0.3
psycopg2 : 2.9.3
jinja2 : 3.1.2
IPython : 8.14.0
pandas_datareader: None
bs4 : 4.12.2
bottleneck : 1.3.7
brotli :
fastparquet : 2023.4.0
fsspec : 2023.6.0
gcsfs : 2023.6.0
matplotlib : 3.7.1
numba : 0.57.0
numexpr : 2.8.4
odfpy : None
openpyxl : 3.1.2
pandas_gbq : None
pyarrow : 12.0.0
pyreadstat : 1.2.2
pyxlsb : 1.0.10
s3fs : 2023.6.0
scipy : 1.10.1
snappy :
sqlalchemy : 2.0.16
tables : 3.8.0
tabulate : 0.9.0
xarray : 2023.5.0
xlrd : 2.0.1
zstandard : 0.19.0
tzdata : 2023.3
qtpy : None
pyqt5 : None

[lithomas1]

Can you build the docs in serial?

Or just build the single problematic page?
python make.py --single getting_started/intro_tutorials/04_plotting.rst

This should give you the exact warning.

[tpaxman]

Thanks @lithomas1, I've done that now. Looks like it might be related to the plt.show() call which is strange as I imagine it typically builds without an issue. Any idea why that would be causing a failure? Looks like adding the :okwarning: flags in a few places solves the issue. See PR #53788. Have not yet rebuilt everything to see if other files are having the same issues. Any idea why this appears to be popping up somewhat sporadically with various rst files?

>>>-------------------------------------------------------------------------
Warning in /home/tpaxman/code/pandas-tpaxman/doc/source/getting_started/intro_tutorials/04_plotting.rst at block ending on line 70
Specify :okwarning: as an option in the ipython:: block to suppress this message
----------------------------------------------------------------------------
<ipython-input-6-1eb00ff78cf2>:1: UserWarning: Matplotlib is currently using agg, which is a non-GUI backend, so cannot show the figure.
  plt.show()
<<<-------------------------------------------------------------------------

Exception occurred:
  File "/home/tpaxman/mambaforge/envs/pandas-dev/lib/python3.10/site-packages/IPython/sphinxext/ipython_directive.py", line 600, in process_input
    raise RuntimeError('Non Expected warning in `{}` line {}'.format(filename, lineno))
RuntimeError: Non Expected warning in `/home/tpaxman/code/pandas-tpaxman/doc/source/getting_started/intro_tutorials/04_plotting.rst` line 70
The full traceback has been saved in /tmp/sphinx-err-_t3ju3ph.log, if you want to report the issue to the developers.
Please also report this if it was a user error, so that a better error message can be provided next time.
A bug report can be filed in the tracker at <https://github.com/sphinx-doc/sphinx/issues>. Thanks!

[lithomas1]

Looks like something wrong with your matplotlib?

Could maybe also be a bad interaction with WSL. Does plotting figures in matplotlib without pandas work at all?

[tpaxman]

@lithomas1 thanks for the feedback. I'll try to see what might be wrong with my WSL then. That's strange that it wasn't giving me issues before so I wonder what I might have changed. If this problem is isolated to me only then I guess this could be closed for now.

[rhshadrach]

I'm experiencing this locally too. This is also #44302.

Could maybe also be a bad interaction with WSL. Does plotting figures in matplotlib without pandas work at all?

I can currently plot with pandas, but when using sphinx I'm guessing a different backend is chosen?

I've added the following code to conf.py

import warnings

warnings.filterwarnings(
    "ignore",
    category=UserWarning,
    message="Matplotlib is currently using agg, which is a"
    " non-GUI backend, so cannot show the figure.",
)

and now the docs build fine - the plots appear as expected.