Documentation graphs are not rendered

[abitrolly]

https://libcst.readthedocs.io/en/latest/why_libcst.html

Diagrams look like this.

[MapleCCC]

I can confirm that I see the same problem on my browser.

By the way, since the last document build is more than 5 months ago, maybe make a fresh document build now is a good idea.

[MapleCCC]

I further investigated the problem. Turn out this bug is related to how the new builder image provided by readthedocs doesn't have the graphviz-dev package pre-installed any more, as elaborated in upstream readthedocs issues 8672 and 8800.

The related readthedocs FAQ entry is seen in "My documentation requires additional dependencies".

The solution, as elaborated on the upstream issues and document, is to set the configuration option build.apt_packages in .readthedocs.yaml to install the graphviz package before document build.

The reason we should choose the graphviz package, instead of other packages whose package names also contain the graphviz keywords, is because it's officially endorsed.

[MapleCCC]

A PR #751 has been opened to fix this issue.