Merged from master.

.gitlab-ci.yml

 ---
+variables:
+  DUNECI_OPTS: "/builds/dune-fem-dg/dune-fem-dg/scripts/opts/ci-gcc.opts"
+
 before_script:
   - duneci-install-module https://gitlab.dune-project.org/core/dune-common.git
   - duneci-install-module https://gitlab.dune-project.org/core/dune-geometry.git
@@ -7,10 +10,6 @@ before_script:
   - duneci-install-module https://gitlab.dune-project.org/extensions/dune-spgrid.git
   - duneci-install-module https://gitlab.dune-project.org/dune-fem/dune-fem.git
 
-debian:10  gcc:c++17:
-  image: duneci/base:10
-  script: duneci-standard-test --opts=/builds/dune-fem-dg/dune-fem-dg/scripts/opts/ci-gcc.opts
-
 #debian:9--gcc:
 #  image: duneci/base:9
 #  script: duneci-standard-test --opts=/builds/dune-fem-dg/dune-fem-dg/scripts/opts/ci-gcc.opts