Blue machine __str__ returned non-string error

Hello all

Im new in HTB, im trying to execute python + ip in HTB pwnbox, but doesnt work.
I trying to pwn the blue machine w/o metasploit.
Someone know about this error?

Target OS: Windows 7 Professional 7601 Service Pack 1
Traceback (most recent call last):
  File "/home/htb-guerohack/MS17-010/", line 55, in <module>
    recvPkt = conn.send_trans(pack('<H', TRANS_PEEK_NMPIPE), maxParameterCount=0xffff, maxDataCount=0x800)
  File "/home/htb-guerohack/MS17-010/", line 262, in send_trans
    self.send_raw(self.create_trans_packet(setup, param, data, mid, maxSetupCount, totalParameterCount, totalDataCount, maxParameterCount, maxDataCount, pid, tid, noPad))
  File "/home/htb-guerohack/MS17-010/", line 259, in create_trans_packet
    return self.create_smb_packet(transCmd, mid, pid, tid)
  File "/home/htb-guerohack/MS17-010/", line 229, in create_smb_packet
    req = str(pkt)
TypeError: __str__ returned non-string (type bytes)