Fix problematic doc build, due to the new builder image provided by readthedocs doesn't has the graphviz-dev package pre-installed any more

[MapleCCC]

This pull request should fix #725.

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.

[codecov-commenter]

Codecov Report

Merging #751 (34474c1) into main (977504f) will not change coverage.
The diff coverage is n/a.

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##             main     #751   +/-   ##
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  Coverage   94.82%   94.82%           
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  Files         247      247           
  Lines       25799    25799           
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  Hits        24463    24463           
  Misses       1336     1336           

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[MapleCCC]

The CI errors are lxml-related. We can safely ignore them for our case here.

[abitrolly]

Adding it as a Python dependency should also work https://pypi.org/project/graphviz/

[MapleCCC]

@abitrolly Thank you for the suggestion. However I am afraid the pypi.org/project/graphviz package is not an option here. The sphinx.ext.graphivz extension, used by libcst to generate graphs in the document, requires a dot command to be present on the $PATH, which the pypi.org/project/graphviz doesn't provide for now.

[zsol]

Thanks @MapleCCC for digging in and fixing the problem. Much appreciated. I'll merge and trigger a doc rebuild now

[zsol]

https://readthedocs.org/projects/libcst/builds/17820520/

[zsol]

aaand, it's live: https://libcst.readthedocs.io/en/latest/why_libcst.html

[abitrolly]

Awesome graphs. :D I didn't pay attention that graphviz is still a wrapper over command line dot. Nice to see it resolved.

[MapleCCC]

@zsol Thanks for your swift work! Glad the document works fine now. 🎉