**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
"""Test DataflowHook is created and the right args are passed to
        start_java_workflow.
        """
        start_java_hook = dataflow_mock.return_value.start_java_dataflow
        gcs_provide_file = gcs_hook.return_value.provide_file
        self.dataflow.check_if_running = CheckJobRunning.IgnoreJob
        self.dataflow.execute(None)
        self.assertTrue(dataflow_mock.called)
        gcs_provide_file.assert_called_once_with(object_url=JAR_FILE)
        start_java_hook.assert_called_once_with(
            job_name=JOB_NAME,
            variables=mock.ANY,
            jar=mock.ANY,
            job_class=JOB_CLASS,
            append_job_name=True,
            multiple_jobs=None,
            on_new_job_id_callback=mock.ANY,
            project_id=None,
            location=TEST_LOCATION
        )
    @mock.patch('airflow.providers.google.cloud.operators.dataflow.DataflowHook')
    @mock.patch('airflow.providers.google.cloud.operators.dataflow.GCSHook')
    def test_check_job_running_exec(self, gcs_hook, dataflow_mock):