add uninstall command for six

.gitlab-ci.yml

@@ -96,6 +96,7 @@ tests:
     - chmod +x ./CI/update_badge.sh
     - ./CI/update_badge.sh > /dev/null
   script:
+    - pip uninstall six
     - pip install -r requirements.txt
     - chmod +x ./CI/run_pytest.sh
     - ./CI/run_pytest.sh
@@ -120,6 +121,7 @@ coverage:
     - chmod +x ./CI/update_badge.sh
     - ./CI/update_badge.sh > /dev/null
   script:
+    - pip uninstall six
     - pip install -r requirements.txt
     - chmod +x ./CI/run_pytest_coverage.sh
     - ./CI/run_pytest_coverage.sh
@@ -142,6 +144,7 @@ sphinx docs:
     - chmod +x ./CI/update_badge.sh
     - ./CI/update_badge.sh > /dev/null
   script:
+    - pip uninstall six
     - pip install -r requirements.txt
     - pip install -r docs/requirements_docs.txt
     - chmod +x ./CI/create_documentation.sh