Update pytest-cov to 3.0.0

[pyup-bot]

This PR updates pytest-cov from 2.12.1 to 3.0.0.

Changelog

3.0.0

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

**Note that this release drops support for Python 2.7 and Python 3.5.**

* Added support for Python 3.10 and updated various test dependencies.
Contributed by Hugo van Kemenade in
`500 <https://github.com/pytest-dev/pytest-cov/pull/500>`_.
* Switched from Travis CI to GitHub Actions. Contributed by Hugo van Kemenade in
`494 <https://github.com/pytest-dev/pytest-cov/pull/494>`_ and
`495 <https://github.com/pytest-dev/pytest-cov/pull/495>`_.
* Add a ``--cov-reset`` CLI option.
Contributed by Danilo Šegan in
`459 <https://github.com/pytest-dev/pytest-cov/pull/459>`_.
* Improved validation of ``--cov-fail-under`` CLI option.
Contributed by ... Ronny Pfannschmidt's desire for skark in
`480 <https://github.com/pytest-dev/pytest-cov/pull/480>`_.
* Dropped Python 2.7 support.
Contributed by Thomas Grainger in
`488 <https://github.com/pytest-dev/pytest-cov/pull/488>`_.
* Updated trove classifiers. Contributed by Michał Bielawski in
`481 <https://github.com/pytest-dev/pytest-cov/pull/481>`_.

2.13.0

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

* Changed the `toml` requirement to be always be directly required (instead of being required through a coverage extra).
This fixes issues with pip-compile (`pip-tools1300 <https://github.com/jazzband/pip-tools/issues/1300>`_).
Contributed by Sorin Sbarnea in `472 <https://github.com/pytest-dev/pytest-cov/pull/472>`_.
* Documented ``show_contexts``.
Contributed by Brian Rutledge in `473 <https://github.com/pytest-dev/pytest-cov/pull/473>`_.

Links

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

[pyup-bot]

Closing this in favor of #341