Intermittent integration test failure: test_mobile_targeting

[jaredlockhart]

Seen here:

https://app.circleci.com/pipelines/github/mozilla/experimenter/42107/workflows/7940d4e2-96cd-4aeb-9cf5-6692239dd146/jobs/215843

Maybe it's trying to query the config before the server has finished starting?

_________ ERROR collecting integration/nimbus/test_mobile_targeting.py _________
/root/.cache/pypoetry/virtualenvs/experimenter_integration_tests-9yJEYhsL-py3.11/lib/python3.11/site-packages/requests/models.py:974: in json
    return complexjson.loads(self.text, **kwargs)
/usr/local/lib/python3.11/json/__init__.py:346: in loads
    return _default_decoder.decode(s)
/usr/local/lib/python3.11/json/decoder.py:337: in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
/usr/local/lib/python3.11/json/decoder.py:355: in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
E   json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

During handling of the above exception, another exception occurred:
experimenter/tests/integration/nimbus/test_mobile_targeting.py:37: in <module>
    @pytest.fixture(params=helpers.load_targeting_configs(app="MOBILE"))
experimenter/tests/integration/nimbus/utils/helpers.py:145: in load_targeting_configs
    config_data = load_config_data()
experimenter/tests/integration/nimbus/utils/helpers.py:34: in load_config_data
    return load_graphql_data(
experimenter/tests/integration/nimbus/utils/helpers.py:24: in load_graphql_data
    ).json()
/root/.cache/pypoetry/virtualenvs/experimenter_integration_tests-9yJEYhsL-py3.11/lib/python3.11/site-packages/requests/models.py:978: in json
    raise RequestsJSONDecodeError(e.msg, e.doc, e.pos)
E   requests.exceptions.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
------------------------------- Captured stderr --------------------------------

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