AWS lambda：pty 设备不足

Question

我尝试在 AWS lambda 中使用 pexpect 库，但收到以下错误：

[ERROR] OSError: out of pty devices

事实证明，任何包含 pty.spawn() 的代码在 lambda 中都会失败。下面是失败的 lambda 的最小代码：

import json
import pty

def lambda_handler(event, context):
    pty.spawn('ls')
    return {
        'statusCode': 200,
        'body': json.dumps('Hello from Lambda!')
    }

等效的期望代码也非常基本：

cmd = f'sftp -i my_key_file -q username@server'
child = pexpect.spawn(cmd, encoding='utf-8')

产生的异常是：

[ERROR] OSError: out of pty devices
Traceback (most recent call last):
   ...

    child = pexpect.spawn(...)
  File "/var/lang/lib/python3.7/site-packages/pexpect/pty_spawn.py", line 205, in __init__
    self._spawn(command, args, preexec_fn, dimensions)
  File "/var/lang/lib/python3.7/site-packages/pexpect/pty_spawn.py", line 304, in _spawn
    cwd=self.cwd, **kwargs)
  File "/var/lang/lib/python3.7/site-packages/pexpect/pty_spawn.py", line 315, in _spawnpty
    return ptyprocess.PtyProcess.spawn(args, **kwargs)
  File "/var/lang/lib/python3.7/site-packages/ptyprocess/ptyprocess.py", line 230, in spawn
    pid, fd = pty.fork()
  File "/var/lang/lib/python3.7/pty.py", line 96, in fork
    master_fd, slave_fd = openpty()
  File "/var/lang/lib/python3.7/pty.py", line 29, in openpty
    master_fd, slave_name = _open_terminal()
  File "/var/lang/lib/python3.7/pty.py", line 59, in _open_terminal
    raise OSError('out of pty devices')
[ERROR] OSError: out of pty devices Traceback (most recent call last):