Drop Python 2 tests

We are going to drop Python 2 completely.

.gitlab-ci.yml

@@ -4,15 +4,7 @@ stages:
   - test
   - pages
 
-python2:
-  stage: test
-  before_script:
-    - pip install .
-    - export LD_LIBRARY_PATH=/usr/local/lib
-  script:
-    - python -m pytest tests
-
-python3:
+pytest:
   stage: test
   before_script:
     - pip3 install .