suppress_warnings with "intersphinx.external" doesn't stop raise with warnings from failing with 5xx error when fetching objects.inv

[tswast]

Describe the bug

Sphinx was failing with an error code despite "intersphinx.external" being included in the suppress_warnings configuration. This is the warning that was causing the failure.

WARNING: failed to reach any of the inventories with the following issues:
intersphinx inventory 'https://pandas.pydata.org/pandas-docs/stable/objects.inv' not fetchable due to <class 'requests.exceptions.HTTPError'>: 522 Server Error: <none> for url: https://pandas.pydata.org/pandas-docs/stable/objects.inv

How to Reproduce

The pandas docs were down the other day. I suppose you could simulate this by setting up a server that raises 5xx errors when hit.

Environment Information

I forgot to capture this yesterday, but here's what I get from CI.

sphinx==9.1.0 sphinx-sitemap==2.9.0 myst-parser==5.0.0 myst-nb==1.4.0 pydata-sphinx-theme==0.16.1

https://github.com/googleapis/python-bigquery-dataframes/actions/runs/23060677881/job/66986134723

Sphinx extensions

extensions = [
    "sphinx.ext.autodoc",
    "sphinx.ext.autosummary",
    "sphinx.ext.intersphinx",
    "sphinx.ext.coverage",
    "sphinx.ext.doctest",
    "sphinx.ext.napoleon",
    "sphinx.ext.todo",
    "sphinx.ext.viewcode",
    "sphinx_sitemap",
    "myst_nb",
]

Additional context

https://github.com/googleapis/python-bigquery-dataframes/blob/main/docs/conf.py