**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
self, mock_conn, mock_controller, mock_uuid
    ):
        launch_method = (
            mock_conn.return_value.
            projects.return_value.
            locations.return_value.
            templates.return_value.
            launch
        )
        launch_method.return_value.execute.return_value = {"job": {"id": TEST_JOB_ID}}
        self.dataflow_hook.start_template_dataflow(  
            job_name=JOB_NAME,
            variables={'region': TEST_LOCATION},
            parameters=PARAMETERS,
            dataflow_template=TEST_TEMPLATE,
            project_id=TEST_PROJECT
        )
        launch_method.assert_called_once_with(
            projectId=TEST_PROJECT,
            location=TEST_LOCATION,
            gcsPath=TEST_TEMPLATE,
            body=mock.ANY,
        )
        mock_controller.assert_called_once_with(