use julia-custom image

.gitlab-ci.yml

-image: julia:1.2
-
-before_script:
-  # workaround for https://github.com/JuliaDocs/Documenter.jl/issues/686
-  - apt-get -qq update; apt-get -y install git git-lfs
-  - git lfs install
-  - git lfs fetch
-  - julia --project=@. -e "import Pkg; Pkg.build()"
+image: git-r3lab.uni.lu:4567/permedcoe/julia-custom
 
 default:
   script: