trying another image for gitlab-ci

.gitlab-ci.yml

 #image: registry.esss.lu.se/ics-docker/miniconda
-image: continuumio/miniconda3
+image: python:3-slim
 .pip_install_default: &pip_install_default
-    - conda install -c anaconda scipy
-    - conda install -c conda-forge matplotlib
-    - conda install -c conda-forge h5py
-    - pip install webdavclient3
+    - pip install scipy matplotlib h5py webdavclient3
 #variables:
 #  TWINE_REPOSITORY_URL: https://artifactory.esss.lu.se/artifactory/api/pypi/ics-pypi
 
@@ -39,9 +36,7 @@ verify_tag:
 pages:
   stage: deploy
   script:
-    - conda install -c conda-forge sphinx
-    - conda install -c conda-forge numpy
-    - pip install sphinxcontrib-blockdiag blockdiag sphinxcontrib-restbuilder sphinx_rtd_theme
+    - pip install sphinx sphinxcontrib-blockdiag blockdiag sphinxcontrib-restbuilder sphinx_rtd_theme numpy
     - pip install git+https://github.com/crossnox/m2r
     - python setup.py install
     - sphinx-build -b html -d public/doctrees   doc public