How to use the freezer.utils.utils.find_executable function in freezer

def log_volume_holding_process(lv):
    try:
        # Let's try to provide more information on the failure
        devices = [i.split("\t") for i in subprocess.check_output([
            utils.find_executable('dmsetup'), "ls"]).splitlines()]
        dev_id = [i[1].strip("()").split(":") for i in devices if
                  lv.split("/").pop() in i[0] and
                  not i[0].endswith("cow")][0]
        command = "{} | grep {},{}".format(
            # lsof is quite long, so no need to add a sleep here
            utils.find_executable('lsof'), dev_id[0], dev_id[1])
        process = subprocess.check_output([command], shell=True)
        LOG.warning("Process holding the volume is '{}'".format(process))
    except Exception as e:
        LOG.warning("Could not get informations on the process holding the"
                    " volume: {}".format(str(e)))

def log_volume_holding_process(lv):
    try:
        # Let's try to provide more information on the failure
        devices = [i.split("\t") for i in subprocess.check_output([
            utils.find_executable('dmsetup'), "ls"]).splitlines()]
        dev_id = [i[1].strip("()").split(":") for i in devices if
                  lv.split("/").pop() in i[0] and
                  not i[0].endswith("cow")][0]
        command = "{} | grep {},{}".format(
            # lsof is quite long, so no need to add a sleep here
            utils.find_executable('lsof'), dev_id[0], dev_id[1])
        process = subprocess.check_output([command], shell=True)
        LOG.warning("Process holding the volume is '{}'".format(process))
    except Exception as e:
        LOG.warning("Could not get informations on the process holding the"
                    " volume: {}".format(str(e)))

def _lvremove(lv):
    for attempt in range(5):
        lvremove_proc = subprocess.Popen(
            '{0} -f {1}'.format(utils.find_executable('lvremove'), lv),
            stdin=subprocess.PIPE,
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE, shell=True,
            executable=utils.find_executable('bash'))
        output, error = lvremove_proc.communicate()
        if lvremove_proc.returncode:
            if "contains a filesystem in use" in error:
                LOG.warning("Couldn't remove volume {0}. "
                            "It is still in use.".format(lv))
                log_volume_holding_process(lv)
            else:
                break
        else:
            return
    # Raise if five attempts made or different error than fs in use
    raise Exception('Unable to remove snapshot {0}. {1}'.format(lv, error))

def get_vol_fs_type(vol_name):
    """
    The argument need to be a full path lvm name i.e. /dev/vg0/var
    or a disk partition like /dev/sda1. The returnet value is the
    file system type
    """
    if os.path.exists(vol_name) is False:
        err = 'Provided volume name not found: {0} '.format(vol_name)
        LOG.exception(err)
        raise Exception(err)

    file_cmd = '{0} -0 -bLs --no-pad --no-buffer --preserve-date \
    {1}'.format(utils.find_executable("file"), vol_name)
    file_process = subprocess.Popen(
        file_cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE,
        stderr=subprocess.PIPE, shell=True,
        executable=utils.find_executable("bash"))
    (file_out, file_err) = file_process.communicate()
    file_match = re.search(r'(\S+?) filesystem data', file_out, re.I)
    if file_match is None:
        err = 'File system type not guessable: {0}'.format(file_err)
        LOG.exception(err)
        raise Exception(err)
    else:
        filesys_type = file_match.group(1)
        LOG.info('File system {0} found for volume {1}'.format(
            filesys_type, vol_name))
        return filesys_type.lower().strip()

def _lvremove(lv):
    for attempt in range(5):
        lvremove_proc = subprocess.Popen(
            '{0} -f {1}'.format(utils.find_executable('lvremove'), lv),
            stdin=subprocess.PIPE,
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE, shell=True,
            executable=utils.find_executable('bash'))
        output, error = lvremove_proc.communicate()
        if lvremove_proc.returncode:
            if "contains a filesystem in use" in error:
                LOG.warning("Couldn't remove volume {0}. "
                            "It is still in use.".format(lv))
                log_volume_holding_process(lv)
            else:
                break
        else:
            return
    # Raise if five attempts made or different error than fs in use
    raise Exception('Unable to remove snapshot {0}. {1}'.format(lv, error))

def _umount(path):
    # Change dir if we are within the mount point to be removed.
    if os.getcwd().startswith(os.path.normpath(path)):
        os.chdir('/')
    umount_proc = subprocess.Popen('{0} -l -f {1}'.format(
        utils.find_executable('umount'), path),
        stdin=subprocess.PIPE,
        stdout=subprocess.PIPE, stderr=subprocess.PIPE,
        shell=True, executable=utils.find_executable('bash'))
    (umount_out, mount_err) = umount_proc.communicate()

    if umount_proc.returncode:
        raise Exception('Impossible to umount {0}. {1}'
                        .format(path, mount_err))
    os.rmdir(path)
    LOG.info('Volume {0} unmounted'.format(path))