build: treat warnings as errors (#564)

* build: treat warnings as errors

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* lint

* add pytest.ini

* add line break

* filter warning which appears only in python 3.7

* filter deprecation warning for grpcio-gcp

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Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>
2 files changed