Bump pytest from 5.0.1 to 6.1.2 (#342)

Bumps [pytest](https://github.com/pytest-dev/pytest) from 5.0.1 to 6.1.2.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/pytest-dev/pytest/compare/5.0.1...6.1.2

)
Signed-off-by: dependabot-preview[bot] <support@dependabot.com>
Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

requirements-dev.txt

 aiohttp==3.5.4
 tox==3.13.2
-pytest==5.0.1
+pytest==6.1.2
 pytest-aiohttp==0.3.0
 pytest-cov==2.7.1
 pytest-runner==5.1