adding libgraphviz-dev to gitlab-ci.yml

.gitlab-ci.yml

@@ -26,7 +26,7 @@ tests:
     stage: tests
     before_script:
         - apt update
-        - apt install -y libgl1-mesa-glx xvfb graphviz xdg-utils libcairo2-dev libjpeg-dev libgif-dev
+        - apt install -y libgl1-mesa-glx xvfb graphviz libgraphviz-dev xdg-utils libcairo2-dev libjpeg-dev libgif-dev
         - wget -nv https://repo.anaconda.com/miniconda/Miniconda3-latest-Linux-x86_64.sh -O /tmp/Miniconda3-latest-Linux-x86_64.sh
         - bash /tmp/Miniconda3-latest-Linux-x86_64.sh -b -p /tmp/miniconda3
         - export PATH=/tmp/miniconda3/bin:$PATH