Change covergae to use pytest.

.gitlab/ci/ubuntu_python.gitlab-ci.yml

@@ -91,7 +91,7 @@ coverage:ubuntu_python:
     - cd ${CI_PROJECT_NAME}
     # Retrieve the installation path of the module, since it is installed with pip.
     - export MODULE_LOCATION=`python -c "import ${CI_PROJECT_NAME} as _; print(_.__path__[0])"`
-    - python -m coverage run --source=$MODULE_LOCATION -m unittest discover -s unit_tests/ -v -b
+    - python -m coverage run --source=$MODULE_LOCATION -m pytest unit_tests/ -v
     - python -m coverage report
     - python -m coverage xml
   coverage: '/(?i)total.*? (100(?:\.0+)?\%|[1-9]?\d(?:\.\d+)?\%)$/'