Bump pytest from 3.6.3 to 5.3.2

Bumps [pytest](https://github.com/pytest-dev/pytest) from 3.6.3 to 5.3.2.
- [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/3.6.3...5.3.2)

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

requirements-dev.txt

@@ -2,6 +2,6 @@ coverage==4.5.4
 ddt==1.2.2
 flake8==3.7.9
 mock==3.0.5
-pytest==5.1.1; python_version >= '3.5'
+pytest==5.3.2; python_version >= '3.5'
 pytest==4.6.5; python_version < '3.5'
 pytest-cov==2.8.1