Update pytest requirement from ~=4.5.0 to ~=4.6.1
Update pytest requirement from ~=4.5.0 to ~=4.6.1

Updates the requirements on [pytest](https://github.com/pytest-dev/pytest) to permit the latest version.
- [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/4.5.0...4.6.1)
ariebovenberg/omgorm,ariebovenberg/snug