'Start the process'

def start(self):

    env = self.get_env()
    cmd = self.cmd
    self.log.info('Spawning    %s', '    '.join((pipes.quote(s) for s in cmd)))
    try:
        self.proc = Popen(self.cmd, env=env, preexec_fn=self.make_preexec_fn(self.user.name), start_new_session=True, cwd=(self.cwd or None))
    except PermissionError:
        script = (shutil.which(cmd[0]) or cmd[0])
        self.log.error('Permission    denied    trying    to    run    %r.    Does    %s    have    access    to    this    file?', script, self.user.name)
        raise
    self.pid = self.proc.pid
