Bumps [pytest-cov](https://github.com/pytest-dev/pytest-cov) from 2.6.0 to 2.8.1.
- [Release notes](https://github.com/pytest-dev/pytest-cov/releases)
- [Changelog](https://github.com/pytest-dev/pytest-cov/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/pytest-dev/pytest-cov/compare/v2.6.0...v2.8.1)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>