How to use the pgctl.fuser.fuser function in pgctl

def clean_service(service_path):
    # we use SIGTERM; SIGKILL is cheating.
    limit = 100
    while limit > 0:  # pragma: no branch: we don't expect to ever hit the limit
        assert os.path.isdir(service_path), service_path
        try:
            show_runaway_processes(service_path)
            print('lock released -- done.')
            break
        except LockHeld:
            print('lock held -- killing!')
            for pid in fuser(service_path):
                try:
                    os.system('ps -fj %i' % pid)
                    os.kill(pid, signal.SIGTERM)
                except OSError as error:  # race condition -- process stopped between list and kill :pragma: no-cover
                    if error.errno == 3:  # no such process
                        pass
                    else:
                        raise
        limit -= 1

def it_kills_processes_holding_the_lock(self, tmpdir):
        lockfile = tmpdir.ensure('lock')
        lock = lockfile.open()
        process = Popen(('sleep', 'infinity'))
        lock.close()

        # assert `process` has `lock`
        assert list(fuser(lockfile.strpath)) == [process.pid]

        with mock.patch('sys.stderr', new_callable=StringIO.StringIO) as mock_stderr:
            terminate_runaway_processes(lockfile.strpath)

        assert 'WARNING: Killing these runaway ' in mock_stderr.getvalue()
        wait_for(lambda: process.poll() == -9)

def on_lock_held(path):
            reraise(LockHeld(
                'another pgctl command is currently managing this service: (%s)\n%s' %
                (bestrelpath(path), ps(fuser(path)))
            ))

def show_runaway_processes(path):
    from .fuser import fuser
    processes = ps(fuser(path))
    if processes:
        raise LockHeld(
            '''\
these runaway processes did not stop:
%s
There are two ways you can fix this:
  * temporarily: pgctl stop %s --force
  * permanently: http://pgctl.readthedocs.org/en/latest/user/quickstart.html#writing-playground-services
''' % (processes, os.path.basename(path))
        )
    else:
        pass

def terminate_runaway_processes(path):
    """forcefully kill processes holding the lock to `path`"""
    from .fuser import fuser
    pids = list(fuser(path))
    processes = ps(pids)
    if processes:
        print_stderr('''[pgctl] WARNING: Killing these runaway processes at user's request (--force):
{}
Learn why they did not stop: http://pgctl.readthedocs.org/en/latest/user/quickstart.html#writing-playground-services
'''.format(processes)
        )

        for pid in pids:
            try:
                os.kill(pid, signal.SIGKILL)
            except OSError:  # pragma: no cover
                # race condition: processes stopped slightly after timeout, before we kill it
                pass