Bump pytest from 3.5.0 to 4.0.2

Bumps [pytest](https://github.com/pytest-dev/pytest) from 3.5.0 to 4.0.2.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@3.5.0...4.0.2)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot-support

requirements-dev.txt

@@ -1,5 +1,5 @@
 flake8==3.6.0
-pytest==3.5.0
+pytest==4.0.2
 pytest-asyncio==0.9.0
 pytest-cov==2.5.1
 pudb==2018.1