Re-enable automatic testing against all Python versions

.gitlab-ci.yml

@@ -1,33 +1,21 @@
-# Official language image. Look for the different tagged releases at:
-# https://hub.docker.com/r/library/python/tags/
+stages:
+- "test"
 
-.job_template: &job_definition
-  # Change pip's cache directory to be inside the project directory since we can
-  # only cache local items.
-  variables:
-    PIP_CACHE_DIR: "$CI_PROJECT_DIR/.cache"
-  
-  # Pip's cache doesn't store the python packages
-  # https://pip.pypa.io/en/stable/reference/pip_install/#caching
-  #
-  # If you want to also cache the installed packages, you have to install
-  # them in a virtualenv and cache it as well.
-  cache:
-    paths:
-      - .cache/pip
-      - venv/
-  
-  before_script:
-    - python -V                  # Print out python version for debugging
-    - pip install virtualenv tox
-    - virtualenv venv
-    - source venv/bin/activate
-    
-  coverage: '/TOTAL.+ ([0-9]{1,3}%)/'
+before_script:
+- python -V
+- pip install wheel tox
 
-py36-dj20:
-  <<: *job_definition
+test-3.5:
+  image: python:3.5-stretch
+  script:  
+  - tox -e py35
+
+test-3.6:
   image: python:3.6-stretch
-  script:
-  - export TOXENV=py36-dj20
-  - tox
+  script:  
+  - tox -e py36
+
+test-3.7:
+  image: python:3.7-stretch
+  script:  
+  - tox -e py37