added -y to apt install. doh.

.gitlab-ci.yml

@@ -26,7 +26,7 @@ tests:
         - apt install -y libgl1-mesa-glx xvfb
         - pip install tox
         - apt install -y graphviz xdg-utils
-        - apt install libcairo2-dev libjpeg-dev libgif-dev
+        - apt install -y libcairo2-dev libjpeg-dev libgif-dev
         - xvfb-run tox -v --recreate
 
 build_and_deploy_docs:
@@ -40,7 +40,7 @@ build_and_deploy_docs:
         - pip install awscli
         - apt update
         - apt install -y graphviz libgl1-mesa-glx xvfb xdg-utils
-        - apt install libcairo2-dev libjpeg-dev libgif-dev
+        - apt install -y libcairo2-dev libjpeg-dev libgif-dev
     script:
         - pip install -r requirements_dev.txt
         - python setup.py install