Bump pytest from 3.7.2 to 3.7.3 in /{{cookiecutter.app_name}}

Bumps [pytest](https://github.com/pytest-dev/pytest) from 3.7.2 to 3.7.3.
- [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/3.7.2...3.7.3

)

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