Conflicting version requirements for coverage between python-coveralls and pytest-cov

[andy-maier]

The latest version of 'python-coveralls' (2.9.1, released 4/2017) requires coverage==4.0.3 (see its setup.py).
The latest version of 'pytest-cov' (2.6.0, released today) requires coverage>=4.4.

This breaks the tests of several of our projects. The version conflicts are reported by pip:

...
python-coveralls 2.9.1 has requirement coverage==4.0.3, but you'll have coverage 4.5.1 which is incompatible.
...
pytest-cov 2.6.0 has requirement coverage>=4.4, but you'll have coverage 4.0.3 which is incompatible.
...

The test run finally breaks when py.test cannot load its pytest-cov plugin:

pluggy.manager.PluginValidationError: Plugin 'pytest_cov' could not be loaded: (coverage 4.0.3 (/home/travis/virtualenv/python2.7.14/lib/python2.7/site-packages), Requirement.parse('coverage>=4.4'))!

Why is it that python-coveralls needs to require exactly coverage==4.0.3? This was doomed to create such a conflict one day.

[inkhey]

Same issue here.

[dkfellows]

As a workaround, just force the version of coverage to be at least 4.4 by pip-installing that over the top; that seems to work with our tests. (OK, they're not thorough tests of whether this is correct, but it seems to work.)