Set a sphinx and / or docutils minimum requirement

[mjpieters]

Your most recent release dropped document.traverse() for document.findall(), which means that your project now assumes that docutils 0.18.1 or newer is used.

However, that also means that the minimum Sphinx version has gone up to 5.0 as only from that version onwards is docutils 0.18 supported. In an older project of mine, supporting older versions and using Sphinx 4.x, can't use sphinxcontrib-spelling 8 now because of this change.

Please either update your version requirements to reflect this. Alternatively, fall back to traverse if findall is not present.