**What happened**:

With the new Backport providers, when calling `DataflowCreatePythonJobOperator` with an empty `py_rerquirments` Dataflow commands always launch inside a virtualenv.

**What you expected to happen**:

The Dataflow command should run locally.


tests/providers/google/cloud/hooks/test_dataflow.py
'tempLocation': 'gs://test/temp'
        }
        self.dataflow_hook.start_template_dataflow(  
            job_name=JOB_NAME, variables=copy.deepcopy(variables), parameters=PARAMETERS,
            dataflow_template=TEST_TEMPLATE, project_id=TEST_PROJECT
        )
        launch_method.assert_called_once_with(
            body={
                'jobName': 'test-dataflow-pipeline-12345678',
                'parameters': PARAMETERS,
                'environment': variables
            },
            gcsPath='gs://dataflow-templates/wordcount/template_file',
            projectId=TEST_PROJECT,
            location=DEFAULT_DATAFLOW_LOCATION,
        )
        mock_controller.assert_called_once_with(
            dataflow=mock_conn.return_value,
            job_id='test-job-id',
            name='test-dataflow-pipeline-12345678',
            num_retries=5,
            poll_sleep=10,
            project_number=TEST_PROJECT,
            location=DEFAULT_DATAFLOW_LOCATION
        )
        mock_controller.return_value.wait_for_done.assert_called_once()
    @mock.patch(DATAFLOW_STRING.format('uuid.uuid4'), return_value=MOCK_UUID)
    @mock.patch(DATAFLOW_STRING.format('_DataflowJobsController'))
    @mock.patch(DATAFLOW_STRING.format('DataflowHook.get_conn'))
    def test_start_template_dataflow_with_custom_region_as_variable(