On our jenkins server when depgraph-view calls dot, dot writes some warning on stderr before it generates the dependency graph picture. And the Launcher object that initiates the call somehow mixes stderr and stdout, so the browser gots a stream that starts with text warnings and continues with the bytes of the picture, and of course the browser doesn't think it's a valid png file. See the result attached. (As a workaround, our sysadmin solved the problem temporarily by sending stderr to /dev/null, so we can see the picture now, but I think it should be fixed in the program.)