CI/CD broken with Coverage 5.0

[nolar]

Expected Behavior

CI/CD works, especially when there are no unrelated code changes.

Actual Behavior

A sample broken build: https://travis-ci.org/zalando-incubator/kopf/builds/625639579

Collecting coveralls (from -r requirements.txt (line 14))
  Downloading https://files.pythonhosted.org/packages/d7/d6/7d32c9c34a621c201c4bb3f61f4c828ee8655f2c7edc3a547e1dea6a7e67/coveralls-1.9.2-py2.py3-none-any.whl

Collecting coverage>=4.4 (from pytest-cov->-r requirements.txt (line 8))
  Downloading https://files.pythonhosted.org/packages/b6/d8/cb3f8bbae33db7f24027721d61f73145f25bfbcf078a23b2998478e5258c/coverage-5.0-cp37-cp37m-manylinux1_x86_64.whl (226kB)

coveralls 1.9.2 has requirement coverage<5.0,>=3.6, but you'll have coverage 5.0 which is incompatible.

Successfully installed PyYAML-5.2 aiohttp-3.6.2 aiojobs-0.2.2 aresponses-1.1.2 async-timeout-3.0.1 asynctest-0.13.0 chardet-3.0.4 click-7.0 codecov-2.0.15 coverage-5.0 coveralls-1.9.2 docopt-0.6.2 freezegun-0.3.12 idna-2.8 iso8601-0.1.12 kopf multidict-4.7.1 mypy-0.740 mypy-extensions-0.4.3 pykube-ng-19.10.0 pytest-aiohttp-0.3.0 pytest-asyncio-0.10.0 pytest-cov-2.8.1 pytest-mock-1.13.0 python-dateutil-2.8.1 requests-2.22.0 typed-ast-1.4.0 typing-extensions-3.7.4.1 urllib3-1.25.7 yarl-1.4.2

Coveralls has a restriction on <5.0 (link), but pip does not respect it.

Since coverage==5.0 has been released 2 days ago on 14.12.2019 (link), it broke coveralls, and thus the Kopf's CI/CD builds.