Update pytest-cov to 2.5.1

[pyup-bot]

There's a new version of pytest-cov available.
You are currently using 2.4.0. I have updated it to 2.5.1

These links might come in handy: PyPI | Changelog | Repo

Changelog

2.5.1

---

• Fixed xdist breakage (regression in 2.5.0).
  Fixes 157 <https://github.com/pytest-dev/pytest-cov/issues/157>_.
• Allow setting custom data_file name in .coveragerc.
  Fixes 145 <https://github.com/pytest-dev/pytest-cov/issues/145>.
  Contributed by Jannis Leidel & Ionel Cristian Mărieș in
  156 <https://github.com/pytest-dev/pytest-cov/pull/156>.

2.5.0

---

• Always show a summary when --cov-fail-under is used. Contributed by Francis Niu in PR141 <https://github.com/pytest-dev/pytest-cov/pull/141>_.
• Added --cov-branch option. Fixes 85 <https://github.com/pytest-dev/pytest-cov/issues/85>_.
• Improve exception handling in subprocess setup. Fixes 144 <https://github.com/pytest-dev/pytest-cov/issues/144>_.
• Fixed handling when --cov is used multiple times. Fixes 151 <https://github.com/pytest-dev/pytest-cov/issues/151>_.

Got merge conflicts? Close this PR and delete the branch. I'll create a new PR for you.

Happy merging! 🤖

[coveralls]

Coverage remained the same at 81.553% when pulling 0180fdc on pyup-update-pytest-cov-2.4.0-to-2.5.1 into dab3f27 on develop.