使用ftp客户端连接，多级目录中带中文会提示异常，无法进入目录

[LostHub]

数组取值dir_name、key_name 异常导致。改为字符串替换可以使用。

Traceback (most recent call last):
File "/usr/local/cos-ftp-server-for-test/venv/lib/python2.7/site-packages/pyftpdlib-1.5.7-py2.7.egg/pyftpdlib/handlers.py", line 1728, in _on_dtp_connection
self.data_channel.push_with_producer(data)
File "/usr/local/cos-ftp-server-for-test/venv/lib/python2.7/site-packages/pyftpdlib-1.5.7-py2.7.egg/pyftpdlib/handlers.py", line 671, in push_with_producer
AsyncChat.push_with_producer(self, producer)
File "/usr/lib64/python2.7/asynchat.py", line 190, in push_with_producer
self.initiate_send()
File "/usr/local/cos-ftp-server-for-test/venv/lib/python2.7/site-packages/pyftpdlib-1.5.7-py2.7.egg/pyftpdlib/handlers.py", line 677, in initiate_send
asynchat.async_chat.initiate_send(self)
File "/usr/lib64/python2.7/asynchat.py", line 226, in initiate_send
data = first.more()
File "/usr/local/cos-ftp-server-for-test/venv/lib/python2.7/site-packages/pyftpdlib-1.5.7-py2.7.egg/pyftpdlib/handlers.py", line 1097, in more
buffer.append(next(self.iterator))
File "/usr/local/cos-ftp-server-for-test/ftp_v5/cos_file_system.py", line 483, in format_mlsx
line = "type=%s;size=%d;perm=%s;modify=%s %s\r\n" % (ft, size, perm, last_modified, name.decode('utf-8'))
File "/usr/lib64/python2.7/encodings/utf_8.py", line 16, in decode
return codecs.utf_8_decode(input, errors, True)
UnicodeDecodeError: 'utf8' codec can't decode byte 0x86 in position 0: invalid start byte