KeyError _is_coroutine on hub.OPT

Given the code:

def _assert_block(hub, test_name: str, test_block: Dict) -> Dict:
    assertion_section_delimiter = test_block.get(
        "assertion_section_delimiter", hub.OPT["validator"]["delimiter"]
    )

and associated test with mock_hub:

def test_assert_block(mock_hub):
    test_name = 'a test'
    test_dict = {"assertion": "assertEqual", "expected_return": "stuff", "assertion_section_delimiter": ":"}
    check._assert_block(mock_hub, test_name, test_dict)

Returns the error

mock_hub = <root..local.share.virtualenvs.mypop-mGqZu586.lib.python3.7.site-packages.pop.mods.pop.testing.MockHub object at 0x7f9937892978>

    def test_assert_block(mock_hub):
        #mock_hub = hub.pop.testing.mock_hub()
        test_name = 'a test'
        test_dict = {"assertion": "assertEqual", "expected_return": "stuff", "assertion_section_delimiter": ":"}
>       check._assert_block(mock_hub, test_name, test_dict)

tests/unit/test_check.py:51: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
validator/validator/check.py:39: in _assert_block
    "assertion_section_delimiter", hub.OPT["validator"]["delimiter"]
/root/.local/share/virtualenvs/mypop-mGqZu586/lib/python3.7/site-packages/pop/mods/pop/testing.py:199: in __getattribute__
    attr = self._orig_to_attr(orig)
/root/.local/share/virtualenvs/mypop-mGqZu586/lib/python3.7/site-packages/pop/mods/pop/testing.py:214: in _orig_to_attr
    attr = self._mock_attr(orig)
/root/.local/share/virtualenvs/mypop-mGqZu586/lib/python3.7/site-packages/pop/mods/pop/testing.py:218: in _mock_attr
    return create_autospec(a, spec_set=True)
/root/.local/share/virtualenvs/mypop-mGqZu586/lib/python3.7/site-packages/asynctest/mock.py:767: in create_autospec
    is_coroutine_func = asyncio.iscoroutinefunction(spec)
/usr/lib/python3.7/asyncio/coroutines.py:163: in iscoroutinefunction
    getattr(func, '_is_coroutine', None) is _is_coroutine)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = {'validator': {'version': False, 'log_file': 'validator.log', 'log_level': 'info', 'log_fmt_logfile': '%(asctime)s,%(m...n': 'basic', 'tests': ('testfile.tst',), 'render': 'jinja|yaml', 'delimiter': ':', 'workers': '5', 'output': 'nested'}}
k = '_is_coroutine'

    def __getattr__(self, k: str):
>       return self.__store[k]
E       KeyError: '_is_coroutine'

/root/.local/share/virtualenvs/mypop-mGqZu586/lib/python3.7/site-packages/pop/mods/pop/data.py:55: KeyError

If in the function being tested, I replace

assertion_section_delimiter = test_block.get(
        "assertion_section_delimiter", hub.OPT["validator"]["delimiter"]
    )

with

assertion_section_delimiter = test_block.get(
        "assertion_section_delimiter", ":"
    )

I don't get the KeyError. So my issue seems to be in the parsing of the mocked hub.OPT (which you can see in the test error output, does contain the expected delimiter key.

What is the appropriate way to mock hub.OPT or otherwise get past the _is_coroutine KeyError?