**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
job = {"id": TEST_JOB_ID, "name": UNIQUE_JOB_NAME, "currentState": DataflowJobStatus.JOB_STATE_DONE}
        mock_list = (
            self.mock_dataflow.projects.return_value.
            locations.return_value.
            jobs.return_value.list
        )
        (
            mock_list.return_value.
            execute.return_value
        ) = {'jobs': [job]}
        (
            self.mock_dataflow.projects.return_value.
            locations.return_value.
            jobs.return_value.
            list_next.return_value
        ) = None
        _DataflowJobsController(
            self.mock_dataflow, TEST_PROJECT,
            TEST_LOCATION, 10, UNIQUE_JOB_NAME).get_jobs()
        mock_list.assert_called_once_with(
            projectId=TEST_PROJECT,
            location=TEST_LOCATION
        )
    def test_dataflow_job_wait_for_multiple_jobs(self):