Cert: Add missing os_utils.py

#!/usr/bin/env python3

#

#   Copyright 2020 - The Android Open Source Project

#

#   Licensed under the Apache License, Version 2.0 (the "License");

#   you may not use this file except in compliance with the License.

#   You may obtain a copy of the License at

#

#       http://www.apache.org/licenses/LICENSE-2.0

#

#   Unless required by applicable law or agreed to in writing, software

#   distributed under the License is distributed on an "AS IS" BASIS,

#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

#   See the License for the specific language governing permissions and

#   limitations under the License.

from pathlib import Path

import subprocess

def is_subprocess_alive(process, timeout_seconds=1):

    """

    Check if a process is alive for at least timeout_seconds

    :param process: a Popen object that represent a subprocess

    :param timeout_seconds: process needs to be alive for at least

           timeout_seconds

    :return: True if process is alive for at least timeout_seconds

    """

    try:

        process.wait(timeout=timeout_seconds)

        return False

    except subprocess.TimeoutExpired as exp:

        return True

def get_gd_root():

    """

    Return the root of the GD test library

    GD root is the parent directory of cert

    :return: root directory string of gd test library

    """

    return str(Path(__file__).absolute().parents[1])