Update pytest-runner to 4.2

[pyup-bot]

This PR updates pytest-runner from 2.11.1 to 4.2.

Changelog

4.2

===

* 40: Remove declared dependency and instead assert it at
run time.

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.

3.0

===

* Dropped support for Python 2.6 and 3.1.

2.12.2

======

* 33: Packaging refresh.

2.12.1

======

* 32: Fix support for ``dependency_links``.

2.12

====

* 30: Rework support for ``--allow-hosts`` and
``--index-url``, removing dependence on
``setuptools.Distribution``'s private member.
Additionally corrects logic in marker evaluation
along with unit tests!

Links

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