graphviz plugin misleading error message

Hi!
I tried `graphviz` plugin on some graphs and saw that it works on some of them but generates an error message "stream closed" and a message about checking if `graphviz` is installed. I could not find any further log.
After some tray-and-fail, I find out the problem is with non-English node ID/Labels, but it was hard to get a clue without any log or comprehensive message.
It would be very helpful to write raw Java exception message somewhere in the logs to debug in such situations.