It's annoying when the tools get in the way. Graphviz is one of my favorite tools, and has been for a couple decades.

Today, though, it failed to use an svg image as a node, saying a plugin was missing. Then googling suggested that installing the ruby svg (librsvg) would solve the problem, but that wouldn't install because a dependency loop in macports.

Finally, installing the packages one-by-one by hand worked. Now, back to what I was doing...