graphviz hangs creating pdf

[blahblahyaya]

From: https://github.com/voormedia/rails-erd
voormedia/rails-erd#63

stringsn88keys commented on Apr 30
I spent a bit of time looking at this, and if you run the command built in ruby-graphviz-1.0.9/lib/graphviz.rb:589 in a separate shell while debugging, the pdf generates just fine.

ruby-graphviz seems to be getting hung up on the call to popen_run in open3.rb ruby 2.1.1 for me. This may need written up in ruby-graphviz (or maybe ruby 2.1, but seems like there would be more problems elsewhere in that case).

We are using
rake erd filetype=dot
dot -Tpdf erd.dot > erd.pdf

as a workaround.