Update pytest-runner to 4.1

[pyup-bot]

This PR updates pytest-runner from 3.0 to 4.1.

Changelog

4.1

===

* 40: Declare dependency on Setuptools in package metadata.

4.0

===

* Drop support for Setuptools before Setuptools 27.3.0.

3.0.1

=====

* 38: Fixed AttributeError when running with ``--dry-run``.
``PyTest.run()`` no longer stores nor returns the result code.
Based on the commit message for `840ff4c <
https://github.com/pytest-dev/pytest-runner/commit/840ff4c2bf6c752d9770f0dd8d64a841060cf9bc>`_,
nothing has ever relied on that value.

Links

• PyPI: https://pypi.python.org/pypi/pytest-runner
• Changelog: https://pyup.io/changelogs/pytest-runner/
• Repo: https://github.com/pytest-dev/pytest-runner

[pyup-bot]

Closing this in favor of #136