**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
#
#
#
#
import unittest
import mock
from airflow.providers.google.cloud.operators.dataflow import (
    CheckJobRunning, DataflowCreateJavaJobOperator, DataflowCreatePythonJobOperator,
    DataflowTemplatedJobStartOperator,
)
from airflow.version import version
TASK_ID = 'test-dataflow-operator'
JOB_NAME = 'test-dataflow-pipeline'
TEMPLATE = 'gs://dataflow-templates/wordcount/template_file'
PARAMETERS = {
    'inputFile': 'gs://dataflow-samples/shakespeare/kinglear.txt',