Penetration Testing Prerequisites Data Exfiltration lab issue

Hello, I’m currently going through the Data Exiltration lab of the Penetration Testing Prerequisites section.
I’ve run into a problem while trying to do the lab. I’m supposed to set up a python server and upload a file to this server from a webshell, using curl.
I’m following the Solution section because of the problem I’ve run into. When I try to upload this file to my python server, I get the following error:

Exception happened during processing of request from (‘’, 35692)
Traceback (most recent call last):
File “/usr/lib/python2.7/”, line 293, in _handle_request_noblock
self.process_request(request, client_address)
File “/usr/lib/python2.7/”, line 321, in process_request
self.finish_request(request, client_address)
File “/usr/lib/python2.7/”, line 334, in finish_request
self.RequestHandlerClass(request, client_address, self)
File “/usr/lib/python2.7/”, line 655, in init
File “/usr/lib/python2.7/”, line 340, in handle
File “/usr/lib/python2.7/”, line 328, in handle_one_request
File “”, line 9, in do_PUT
lenght = int(self.headers[‘content-lenght’])
File “/usr/lib/python2.7/”, line 393, in getitem
return self.dict[name.lower()]
KeyError: ‘content-lenght’

Nothing I do seems to work. I’ve seen some videos of people going through this same lab, doing everything exactly the same as I am and it works for them.
Any help would be appreciated. I could just mark the lab as completed, since I already know what I’m supposed to do, but I want to get the flag and know what’s happening.