**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.
        """
        dataflow_running = dataflow_mock.return_value.is_job_dataflow_running
        dataflow_running.return_value = True
        start_java_hook = dataflow_mock.return_value.start_java_dataflow
        gcs_provide_file = gcs_hook.return_value.provide_file
        self.dataflow.check_if_running = True
        self.dataflow.execute(None)
        self.assertTrue(dataflow_mock.called)
        gcs_provide_file.assert_not_called()
        start_java_hook.assert_not_called()
        dataflow_running.assert_called_once_with(
            name=JOB_NAME, variables=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_not_running_exec(self, gcs_hook, dataflow_mock):