Bump pytest from 3.2.5 to 5.3.5

Bumps [pytest](https://github.com/pytest-dev/pytest) from 3.2.5 to 5.3.5.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@3.2.5...5.3.5)

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

Author: dependabot-preview[bot]

requirements-test.txt

@@ -4,7 +4,7 @@ tox
 
 flake8==3.7.9
 
-pytest==3.2.5
+pytest==5.3.5
 coverage
 pytest-expect>=1.1,<2.0
 mock