Update pytest-cov to 2.8.1

[pyup-bot]

This PR updates pytest-cov from 2.7.1 to 2.8.1.

Changelog

2.8.1

------------------

* Fixed `348 <https://github.com/pytest-dev/pytest-cov/issues/348>`_ -
regression when only certain reports (html or xml) are used then ``--cov-fail-under`` always fails.

2.8.0

------------------

* Fixed ``RecursionError`` that can occur when using
`cleanup_on_signal <https://pytest-cov.readthedocs.io/en/latest/subprocess-support.htmlif-you-got-custom-signal-handling>`__ or
`cleanup_on_sigterm <https://pytest-cov.readthedocs.io/en/latest/subprocess-support.htmlif-you-got-custom-signal-handling>`__.
See: `294 <https://github.com/pytest-dev/pytest-cov/issues/294>`_.
The 2.7.x releases of pytest-cov should be considered broken regarding aforementioned cleanup API.
* Added compatibility with future xdist release that deprecates some internals
(match pytest-xdist master/worker terminology).
Contributed by Thomas Grainger in `321 <https://github.com/pytest-dev/pytest-cov/pull/321>`_
* Fixed breakage that occurs when multiple reporting options are used.
Contributed by Thomas Grainger in `338 <https://github.com/pytest-dev/pytest-cov/pull/338>`_.
* Changed internals to use a stub instead of ``os.devnull``.
Contributed by Thomas Grainger in `332 <https://github.com/pytest-dev/pytest-cov/pull/332>`_.
* Added support for Coverage 5.0.
Contributed by Ned Batchelder in `319 <https://github.com/pytest-dev/pytest-cov/pull/319>`_.
* Added support for float values in ``--cov-fail-under``.
Contributed by Martín Gaitán in `311 <https://github.com/pytest-dev/pytest-cov/pull/311>`_.
* Various documentation fixes. Contributed by
Juanjo Bazán,
Andrew Murray and
Albert Tugushev in
`298 <https://github.com/pytest-dev/pytest-cov/pull/298>`_,
`299 <https://github.com/pytest-dev/pytest-cov/pull/299>`_ and
`307 <https://github.com/pytest-dev/pytest-cov/pull/307>`_.
* Various testing improvements. Contributed by
Ned Batchelder,
Daniel Hahler,
Ionel Cristian Mărieș and
Hugo van Kemenade in
`313 <https://github.com/pytest-dev/pytest-cov/pull/313>`_,
`314 <https://github.com/pytest-dev/pytest-cov/pull/314>`_,
`315 <https://github.com/pytest-dev/pytest-cov/pull/315>`_,
`316 <https://github.com/pytest-dev/pytest-cov/pull/316>`_,
`325 <https://github.com/pytest-dev/pytest-cov/pull/325>`_,
`326 <https://github.com/pytest-dev/pytest-cov/pull/326>`_,
`334 <https://github.com/pytest-dev/pytest-cov/pull/334>`_ and
`335 <https://github.com/pytest-dev/pytest-cov/pull/335>`_.
* Added the ``--cov-context`` CLI options that enables coverage contexts. Only works with coverage 5.0+.
Contributed by Ned Batchelder in `345 <https://github.com/pytest-dev/pytest-cov/pull/345>`_.

Links

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