Add pytest dependency to mypy GitLab job

.gitlab-ci.yml

@@ -57,7 +57,7 @@ mypy:
   tags: [ docker ]
   stage: linting
   script:
-    - pip install mypy types-PyYAML types-jsonschema types-requests types-setuptools types-lxml types-python-dateutil
+    - pip install mypy types-PyYAML types-jsonschema types-requests types-setuptools types-lxml types-python-dateutil pytest
     - make mypy
   allow_failure: true