Fix errno 3 when stopping host handler.

import os

import sys

import pty

import errno

import fcntl

import subprocess

import logging

    def stop(self):

        # kill all currently running shells

        for shell in self.shells.values():

            try:

                shell.kill()

            except OSError as exc:

                if exc.errno != errno.ESRCH:

                    raise

                # process does not exists

            shell.close_cb()

        self.shells.clear()

        BasePlugin.stop(self)