Merge branch 'bugfix/graphviz-draw' into 'master'

Adjust use of libgvc to fix two graphviz_draw issues

Closes #597

See merge request !34
2 jobs for master in 143 minutes and 5 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #4870
amd64
job_clang_amd64

02:23:05

passed #4869
amd64
job_gcc_amd64

02:02:34