c82190cdb6 tests: Add Python dead code linter (vulture) (practicalswift)
590a57fdec tests: Remove unused testing code (practicalswift)
Pull request description:
Add Python dead code linter (`vulture`) to Travis.
Rationale for allowing dead code only after explicit opt-in (via `--ignore-names`):
* Less is more :-)
* Unused code is by definition "untested"
* Unused code can be an indication of bugs/logical errors. By making the contributor aware of newly introduced unused code it gives him/her an opportunity to investigate if the unused code they introduce is malignant or benign :-)
* Unused code is hard to spot for humans and is thus often missed during manual review
* [YAGNI](https://en.wikipedia.org/wiki/You_aren%27t_gonna_need_it)
Based on #14312 to make linter job pass.
Tree-SHA512: 4c581df7c34986e226e4ade479e0d3c549daf38f4a4dc4564b25564d63e773a1830ba55d1289c771b1fa325483e8855b82b56e61859fe8e4b7dfa54034b093b6
