[ci] Add pyopencl and headers

.gitlab-ci.yml

 py_testproject:
   type: test
   image: docker-registry.esrf.fr/dau/x11:python3.7_buster
+  before_script:
+    - apt-get update -qq && apt-get install -y -qq ocl-icd-opencl-dev opencl-c-headers opencl-clhpp-headers opencl-headers
+    # - apt-get update -qq && apt install -qq -y ocl-icd-libopencl1
+    - export SILX_OPENCL=1
   script:                   # Run the tests from the installed module
     - python -m pip install --upgrade pip
     - pip install --upgrade setuptools wheel

requirements.txt

@@ -4,3 +4,4 @@ PyQt5==5.13.2
 opencv-python
 scikit-image
 orange3==3.22.0
+pyopencl