[bugfix][CI] Improve CI config.

.gitlab-ci.yml

 ---
+variables:
+  DUNECI_OPTS:       $CI_PROJECT_DIR/scripts/opts/ci-gcc.opts
+  # dune-python will use DUNE_OPTS when building stuff
+  DUNE_OPTS:         $CI_PROJECT_DIR/scripts/opts/ci-gcc.opts
+  DUNECI_TOOLCHAIN:  gcc-7-17
+  DUNE_CONTROL_PATH: /duneci/modules:$CI_PROJECT_DIR
+  DUNE_PY_DIR:       /duneci/modules/dune-py
+  PYTHONPATH:        "/duneci/modules/dune-python/build-cmake/python:/duneci/modules/dune-fem/build-cmake/python:/duneci/modules/dune-alugrid/build-cmake/python:$CI_PROJECT_DIR/build-cmake/python"
+
 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
@@ -13,36 +22,8 @@ before_script:
 debian-10-gcc-8-17:
   image: duneci/debian:10
   script: duneci-standard-test
-  #variables: 
-  # DUNECI_OPTS: /duneci/opts.gcc.c++17
-  #    # allow expensive tests
-  variables:
-    DUNECI_CXXFLAGS: -mavx
-    DUNECI_TEST_LABELS: ""
-    DUNECI_TOOLCHAIN: gcc-7-17
-    DUNE_TEST_EXPECTED_VC_IMPLEMENTATION: AVX
-    #CMAKE_DISABLE_FIND_PACKAGE_Vc: TRUE
-    #CMAKE_DISABLE_FIND_PACKAGE_Alberta: TRUE
 
 ubuntu:18.04--gcc:
   image: duneci/ubuntu:18.04
   script: duneci-standard-test
-  variables:
-    DUNECI_TOOLCHAIN: gcc-7-17
-
-#ubuntu:18.04--clang:
-#  image: duneci/ubuntu:18.04
-#  script: duneci-standard-test
-#  variables: {DUNECI_OPTS: /duneci/opts.clang}
 
-#ubuntu:18.04--python:
-#  image: duneci/ubuntu:18.04
-#  variables: {DUNECI_OPTS: /duneci/opts.gcc}
-# script:
-#  - cd /duneci/modules/
-#  - export DUNE_PY_DIR=${PWD}/cache/
-#  - export PYTHONPATH=${PWD}/dune-python/build-cmake/python:${PWD}/dune-alugrid/build-cmake/python:${PWD}/dune-fem/build-cmake/python:${PWD}/dune-fem/build-cmake/python:${PWD}/dune-fem-dg/build-cmake/python:${PWD}/dune-polygongrid/build-cmake/python:${PWD}/dune-spgrid/build-cmake/python:${PWD}/dune-vem/build-cmake/python:${PWD}/opm-grid/build-cmake/python
-#  - dunecontrol
-#  - cd /duneci/modules/dune-fem-dg/pydemo/euler
-#  - python paper.py
-#variables: {DUNECI_OPTS: /duneci/opts.clang}

pydemo/euler/CMakeLists.txt

 # add custom target to build tool chain for euler
-#add_custom_target(euler_python
-#                  COMMAND ${PYTHON_EXECUTABLE} main.py
-#                  WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})
-
-# add custom target to build tool chain for euler
-#add_test(NAME euler_python
-#         COMMAND ${PYTHON_EXECUTABLE} test.py
-#         WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})
+add_test(NAME euler_python
+         COMMAND ${PYTHON_EXECUTABLE} test.py
+         WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})