Some tests are failing with Pytest 4

[okin]

Calling fixtures directly is not supported with pytest 4.
Running the tests with pytest 4 leads to en error like the following:

request = <SubRequest 'pdep_manager' for <Function 'test_get_set[JsonDB]'>>

    @pytest.fixture(params=[JsonDB, DbmDB, SqliteDB])
    def pdep_manager(request):
>       return dep_manager(request)
E       _pytest.warning_types.RemovedInPytest4Warning: Fixture "dep_manager" called directly. Fixtures are not meant to be called directly, are created automatically when test functions request them as parameters. See https://docs.pytest.org/en/latest/fixture.html for more information.

tests/test_dependency.py:71: RemovedInPytest4Warning

In this case the tests have been run with pytest==4.0.2.

[koobs]

After backporting the fixes in 08e9c0b, I'm seeing the following fixture related error:

platform freebsd13 -- Python 3.6.8, pytest-4.5.0, py-1.8.0, pluggy-0.11.0 -- /usr/local/bin/python3.6

ERROR collecting tests/test_dependency.py
__________________________________________________________________
tests/test_dependency.py:72: in <module>
    pytest.fixture(params=[JsonDB, DbmDB, SqliteDB])(pdep_manager)
/usr/local/lib/python3.6/site-packages/_pytest/fixtures.py:986: in __call__
    "fixture is being applied more than once to the same function"
E   ValueError: fixture is being applied more than once to the same function

Related issues:

pytest-dev/pytest#3518
kevin1024/pytest-httpbin#49
pytest-dev/pytest#2334