**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.


airflow/providers/google/cloud/hooks/dataflow.py
"""
        Waits for Dataflow job to complete.
        :return: Job id
        :rtype: Optional[str]
        """
        self.log.info("Start waiting for DataFlow process to complete.")
        self.job_id = None
        reads = [self._proc.stderr, self._proc.stdout]
        while True:
            
            readable_fds, _, _ = select.select(reads, [], [], 5)
            if readable_fds is None:
                self.log.info("Waiting for DataFlow process to complete.")
                continue
            for readable_fd in readable_fds:
                self._process_fd(readable_fd)
            if self._proc.poll() is not None:
                break
        
        for readable_fd in reads:
            self._process_fd(readable_fd)
        self.log.info("Process exited with return code: %s", self._proc.returncode)
        if self._proc.returncode != 0:
            raise Exception("DataFlow failed with return code {}".format(self._proc.returncode))
        return self.job_id
class DataflowHook(GoogleBaseHook):