Spanner: 'TestSpannerClient.test_client_with_grpc_gcp_channel' unit test fails repeatably

[tseaver]

When running the full nox suite, tripped over these errors in the unit_grpc_gcp sessions:

_____________ TestSpannerClient.test_client_with_grpc_gcp_channel ______________

self = <test_spanner_client_v1.TestSpannerClient object at 0x7f557d8ea668>
grpc_gcp_secure_channel = <MagicMock name='secure_channel' id='140005155447752'>
api_config = <MagicMock name='ApiConfig' id='140005155467504'>
merge = <MagicMock name='Merge' id='140005155827784'>
auth_default = <MagicMock name='default' id='140005155256136'>

    @pytest.mark.skipif(not spanner_v1.HAS_GRPC_GCP,
                        reason='grpc_gcp module not available')
    @mock.patch(
        'google.auth.default',
        return_value=(mock.sentinel.credentials, mock.sentinel.projet))
    @mock.patch('google.protobuf.text_format.Merge')
    @mock.patch('grpc_gcp.proto.grpc_gcp_pb2.ApiConfig',
                return_value=mock.sentinel.api_config)
    @mock.patch('grpc_gcp.secure_channel')
    def test_client_with_grpc_gcp_channel(self,
                                          grpc_gcp_secure_channel,
                                          api_config,
                                          merge,
                                          auth_default):
        spanner_target = 'spanner.googleapis.com:443'
        client = spanner_v1.SpannerClient()
        merge.assert_called_once_with(mock.ANY, mock.sentinel.api_config)
        options = [('grpc_gcp.api_config', mock.sentinel.api_config)]
        grpc_gcp_secure_channel.assert_called_once_with(
>           spanner_target, mock.ANY, options=options)

tests/unit/gapic/v1/test_spanner_client_v1.py:578: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

_mock_self = <MagicMock name='secure_channel' id='140005155447752'>
args = ('spanner.googleapis.com:443', <ANY>)
kwargs = {'options': [('grpc_gcp.api_config', sentinel.api_config)]}
self = <MagicMock name='secure_channel' id='140005155447752'>
msg = "Expected 'secure_channel' to be called once. Called 0 times."

    def assert_called_once_with(_mock_self, *args, **kwargs):
        """assert that the mock was called exactly once and with the specified
            arguments."""
        self = _mock_self
        if not self.call_count == 1:
            msg = ("Expected '%s' to be called once. Called %s times." %
                   (self._mock_name or 'mock', self.call_count))
>           raise AssertionError(msg)
E           AssertionError: Expected 'secure_channel' to be called once. Called 0 times.

.nox/unit-grpc-gcp-3-7/lib/python3.7/site-packages/mock/mock.py:947: AssertionError

And a side note: there is really no purpose in running with grpcio-gcp on all supported Pythons: we should trim it back to just 2.7 and 3.6.

[tseaver]

Looks like we need a new release of api_core: the gprc_gcp stuff added in #5533 is not in a release. @crwilcox Can you do that release?

[tseaver]

PR #5865 solves this issue by using development installs of the local packages during nox unit / system test runs.