Test suite fails against Pytest 5

[stanislavlevin]

I run the 'custodia' test suite with Pytest 5:

138 passed, 1 skipped, 1 warnings, 23 error

There are several identical errors:

==================================== ERRORS ====================================
_______________ ERROR at setup of TestBasics.test_default_answer _______________

self = <functional.test_basics.TestBasics object at 0x7fa1f58e4080>
simple_configuration = None
request = <SubRequest 'custodia_server' for <Function test_default_answer>>
dev_null = 4

    @pytest.fixture(scope="class")
    def custodia_server(self, simple_configuration, request, dev_null):
        # Don't write server messages to stdout unless we are in debug mode
        # pylint: disable=no-member
>       if pytest.config.getoption('debug') or \
                pytest.config.getoption('verbose'):
E               pytest.PytestDeprecationWarning: the `pytest.config` global is deprecated.  Please use `request.config` or `pytest_configure` (if you're a pytest plugin) instead.

tests/functional/base.py:101: PytestDeprecationWarning

[simo5]

Handled in #246