Update .gitlab-ci.yml to use pytest

.gitlab-ci.yml

+image: python:3.6
+
 stages:
-  - build
+ - test
+
+before_script:
+  - pip3 install .
+  - pip3 show myapp
 
-PythonBuild:
-  stage: build
-  artifacts:
-    untracked: true
+run tests:
+  stage: test
+  only:
+    - develop
+  tags:
+    - python3
+    - test
   script:
-    - apt-get update && apt-get install python3 -y
+    - pytest test
\ No newline at end of file