Bump pytest from 4.5.0 to 4.6.1 (#240)

Bumps [pytest](https://github.com/pytest-dev/pytest) from 4.5.0 to 4.6.1.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@4.5.0...4.6.1)

Author: dependabot-preview[bot]

dev-requirements.txt

@@ -1,5 +1,5 @@
 -r requirements.txt
 coverage
-pytest==4.5.0
+pytest==4.6.1
 pytest-asyncio==0.10.0
 pytest-aiohttp==0.3.0