How to solve "IOError: [Errno 2] There is no such file or directory: 'resources / ch06-mailboxes / data / orthpole.mbox'"?

import mailbox
import email
import json

MBOX = 'resources/ch06-mailboxes/data/orthpole.mbox'



def objectify_message(msg):

# Map in fields from the message
o_msg = dict([ (k, v) for (k,v) in msg.items() ])

# Assume one part to the message and get its content
# and its content type

part = [p for p in msg.walk()][0]
o_msg['contentType'] = part.get_content_type()
o_msg['content'] = part.get_payload()

return o_msg


 mbox = mailbox.UnixMailbox(open(MBOX, 'rb'), email.message_from_file)

 messages = []

 while 1:
   msg = mbox.next()

   if msg is None: break

       messages.append(objectify_message(msg))

       print json.dumps(messages, indent=1)

IOError Traceback (last last call) in () # messages in a convenient JSON view

mbox = mailbox.UnixMailbox (open (MBOX, 'rb'), email.message_from_file)

messages = []

IOError: [Errno 2] There is no such file or directory: 'resources / ch06-mailboxes / data / orthpole.mbox'