graceful fail of not finding graphviz dot binary

[kyleomalley]

Would it be possible to handle a condition where dot is not found and generate (or reference) an image stating something like "install graphviz, dot not found". currently markdown i think just crashes and the entire page doesn't get rendered. actually, even just a broken image would be okay for me.

it would also be really useful to be able to specify multiple paths for the dot binary like the code you showed me earlier.

The problem that I have is that the systems running this plugin will be either linux or osx and most will not have dot installed

[sprin]

Both should be possible:

• display an error in the rendered doc when the binary is not found.
• generally, improve cross-platform support, and specifically, use a more robust technique to locate the binary on different platforms.

If this request is related to a commercial project, are you willing to pay for the work? If this related to an OSS project, I have limited bandwidth, but show me your project and I'll see when I can make some time.

Of course, pull requests accepted.