**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/operators/test_dataflow.py
def setUp(self):
        self.dataflow = DataflowCreateJavaJobOperator(
            task_id=TASK_ID,
            jar=JAR_FILE,
            job_name=JOB_NAME,
            job_class=JOB_CLASS,
            dataflow_default_options=DEFAULT_OPTIONS_JAVA,
            options=ADDITIONAL_OPTIONS,
            poll_sleep=POLL_SLEEP,
            location=TEST_LOCATION
        )
    def test_init(self):
        """Test DataflowTemplateOperator instance is properly initialized."""
        self.assertEqual(self.dataflow.task_id, TASK_ID)
        self.assertEqual(self.dataflow.job_name, JOB_NAME)
        self.assertEqual(self.dataflow.poll_sleep, POLL_SLEEP)
        self.assertEqual(self.dataflow.dataflow_default_options,
                         DEFAULT_OPTIONS_JAVA)
        self.assertEqual(self.dataflow.job_class, JOB_CLASS)
        self.assertEqual(self.dataflow.jar, JAR_FILE)
        self.assertEqual(self.dataflow.options,
                         EXPECTED_ADDITIONAL_OPTIONS)
        self.assertEqual(self.dataflow.check_if_running, CheckJobRunning.WaitForRun)
    @mock.patch('airflow.providers.google.cloud.operators.dataflow.DataflowHook')
    @mock.patch('airflow.providers.google.cloud.operators.dataflow.GCSHook')
    def test_exec(self, gcs_hook, dataflow_mock):