doc: Install graphviz

Fixes `WARNING: dot command 'dot' cannot be run (needed for graphviz output), check the graphviz_dot setting`

Signed-off-by: David Galloway <dgallowa@redhat.com>

diff --git a/.readthedocs.yml b/.readthedocs.yml
index 361c664fa22cd3864522af8e91c11e9722fd0cb0..8fcdfee9326671c4f0fff44f500b6d4ab2acc5ed 100644 (file)
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -14,6 +14,7 @@ build:
     python: "3.8"
   apt_packages:
     - ditaa
+    - graphviz
   jobs:
     pre_build:
       - bash admin/rtd-checkout-main