Fail on warnings by default: even from CLI, not only in Travis CI

.travis.yml

@@ -39,10 +39,10 @@ before_script:
   - tools/kubernetes-client.sh
 
 script:
-  - pytest -Werror --cov=kopf --cov-branch
+  - pytest --cov=kopf --cov-branch
   - coveralls
   - codecov --flags unit
-  - pytest -Werror --only-e2e  # NB: after the coverage uploads!
+  - pytest --only-e2e  # NB: after the coverage uploads!
   - mypy kopf --strict --pretty
 
 deploy:

tests/conftest.py

@@ -26,6 +26,9 @@ def pytest_configure(config):
     config.addinivalue_line('markers', "e2e: end-to-end tests with real operators.")
     config.addinivalue_line('markers', "resource_clustered: (internal parameterizatiom mark).")
 
+    # Unexpected warnings should fail the tests. Use `-Wignore` to explicitly disable it.
+    config.addinivalue_line('filterwarnings', 'error')
+
 
 def pytest_addoption(parser):
     parser.addoption("--only-e2e", action="store_true", help="Execute end-to-end tests only.")