[conda_build_config] Add graphviz variable to satisfy (test dependencies)...

[conda_build_config] Add graphviz variable to satisfy (test dependencies) bob.ip.binseg and bob.med.tb (at least)
2 jobs for add-graphviz in 37 minutes and 16 seconds
Status Job ID Name Coverage
  Build
passed #243254
docker
build_linux

00:18:19

4.0%
passed #243255
intel macos
build_macos_intel

00:37:16

4.0%