Bump pytest from 5.1.0 to 5.1.1

Bumps [pytest](https://github.com/pytest-dev/pytest) from 5.1.0 to 5.1.1.
- [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/5.1.0...5.1.1)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

requirements-dev.txt

@@ -7,7 +7,7 @@ flake8==3.7.8
 flake8-type-annotations==0.1.0
 flake8-tidy-imports==2.0.0
 mypy==0.720
-pytest==5.1.0
+pytest==5.1.1
 pytest-asyncio==0.10.0
 pytest-cov==2.7.1
 pytest-mock==1.10.4