Add basic cli tests for date/time options and fix build warnings

[davidag]

Inspired by tests in #282 (which is sadly stalled), here are some basic tests for testing date/time correctness for all Watson commands which do have time-related options.

Besides that, a mock deprecation warning has been fixed by using mocker. It was a trivial replace, that's why I've decided to add it to this PR, although in a separate commit.

The message in the builds was as follows:

DeprecationWarning: "mock" fixture has been deprecated, use "mocker" instead
    '"mock" fixture has been deprecated, use "mocker" instead', DeprecationWarning

-- Docs: https://docs.pytest.org/en/latest/warnings.html

A pytest warning related to the datafiles plugin has also been fixed. The message was as follows:

.tox/py36/lib/python3.6/site-packages/_pytest/mark/structures.py:324

/home/travis/build/TailorDev/Watson/.tox/py36/lib/python3.6/site-packages/_pytest
/mark/structures.py:324: PytestUnknownMarkWarning: Unknown pytest.mark.datafiles - 
    is this a typo?  You can register custom marks to avoid this warning -
    for details, see https://docs.pytest.org/en/latest/mark.html

    PytestUnknownMarkWarning,

This PR also includes changes from PR #315 as they are necessary to run green. When that PR is merged, I will rebase and leave only the other commits, if that's OK for you ☺️

Update 2019-09-30: This PR is now ready to be code-reviewed / merged.

[davidag]

@jmaupetit Thanks to you merging #315 I've been able to remove the unneeded commit in this PR, and it should be ready to be code-reviewed / merged.

[k4nar]

Thanks for taking the time to do that!

The way you structured the tests is a bit unusual, at least to my eyes. Are you following a known pattern, or is it just something you came up with? :)

No judgment involved, I would be happy to refactor it in what I think would be a more conventional way if you'd like.

[davidag]

Thanks for taking the time to do that!

No problem!

The way you structured the tests is a bit unusual, at least to my eyes. Are you following a known pattern, or is it just something you came up with? :)

I'm not sure I understand what you mean 😅 Is the hierarchy what looks unusual to you? I remember I programmed this trying to refactor code after adding each test in order to avoid duplicate code.

In any case, there's no pattern here, just what I came up with ☺️

No judgment involved, I would be happy to refactor it in what I think would be a more conventional way if you'd like.

Please, go ahead! I'm sure the tests will be more consistent and thorough if you could give me a hand here 👍

[davidag]

@k4nar If it's of any help, I wouldn't mind refactoring the tests into a more usual structure if you pointed me to some example/reference code.

Thank you for your time and excuse my insistence!

[davidag]

@k4nar: I've removed inheritance to make the tests more "pytesty" 🤞 ☺️

[k4nar]

Great work thanks! Sorry for never taking the time to go back to you :( .