Limit doctest to non-init files

.gitlab-ci.yml

@@ -9,7 +9,7 @@ doctest:
   image: python:3.7
   script:
     - pip install -r requirements.txt
-    - python -m doctest -v freeforestml/*.py
+    - "python -m doctest -v $(ls freeforestml/*.py | grep -v '__init__.py')"
 
 unittest:
   stage: test