gitlab-ci: Run unit tests with 'tox'

Signed-off-by: Vasilis Tsiligiannis <acinonyx@openwrt.gr>

.gitlab-ci.yml

@@ -43,10 +43,10 @@ build3:
 test:
   stage: test
   image: python:2.7
+  before_script:
+    - pip install tox
   script:
-    - pip install --no-cache-dir --no-deps -r requirements-dev.txt
-    - cp env-dist .env
-    - pytest
+    - tox -e pytest
 docker:
   stage: deploy
   image: docker:latest