ReadTheDocs builds are failing

[dhalbert]

RTD builds are failing due to a new policy by RTD of failing builds when the PDF generation fails:
example: https://readthedocs.org/projects/circuitpython/builds/19783677/

Error
PDF generation failed. The build log below contains information on what errors caused the failure.Our code has recently changed to fail the entire build on PDF errors, where we used to pass the build when a PDF was created.Please contact us if you need help understanding this error.

! LaTeX Error: Unknown graphics extension: .svg.

We are loading svg support, but it's not working:

WARNING: RSVG converter command 'rsvg-convert' cannot be run. Check the rsvg_converter_bin setting

Here is the whole raw log:
rtd-fail.txt

[dhalbert]

The HTML part of the build is working and is available on RTD, so the PDF failure is not causing the whole build to fail.

[dhalbert]

This problem seems to have gone away, e.g.: https://readthedocs.org/projects/circuitpython/builds/19833832/ did not fail.