I've been using this extension since before it was abandoned. Got it working again on 1.37.1 using this patchset
Topic on Extension talk:GraphViz
How did you use/install the pachset?
You can download the entire patched extension or you can download just the diff.patch and apply it to the unpatched extension
Thank you. Very useful extension for which there was no replacement. After upgrade to 1.37.1 it was possible to resurrect the generated pictures from images directory and keep the pages but impossible to create new ones. Now it works again.