I have a script that I found on the internet that worked in Python 3.4, but not Python 3.5. I'm not too familiar in python, but it has the 

#!/usr/bin/env python3

schlebang at the top of the file. And it also throws this exception when I try to run it:
Traceback (most recent call last):

File "/home/username/folder/script.py", line 18, in 
doc = opener.open(url)
File "/usr/lib/python3.5/urllib/request.py", line 472, in open
response = meth(req, response)
File "/usr/lib/python3.5/urllib/request.py", line 582, in http_response
      'http', request, response, code, msg, hdrs)
File "/usr/lib/python3.5/urllib/request.py", line 504, in error
result = self._call_chain(*args)
File "/usr/lib/python3.5/urllib/request.py", line 444, in _call_chain
result = func(*args)
File "/usr/lib/python3.5/urllib/request.py", line 968, in http_error_401
      url, req, headers)
File "/usr/lib/python3.5/urllib/request.py", line 921, in http_error_auth_reqed
return self.retry_http_basic_auth(host, req, realm)
File "/usr/lib/python3.5/urllib/request.py", line 931, in retry_http_basic_auth
return self.parent.open(req, timeout=req.timeout)
File "/usr/lib/python3.5/urllib/request.py", line 472, in open
response = meth(req, response)
File "/usr/lib/python3.5/urllib/request.py", line 582, in http_response
      'http', request, response, code, msg, hdrs)
File "/usr/lib/python3.5/urllib/request.py", line 510, in error
      return self._call_chain(*args)
File "/usr/lib/python3.5/urllib/request.py", line 444, in _call_chain
      result = func(*args)
File "/usr/lib/python3.5/urllib/request.py", line 590, in http_error_default
raise HTTPError(req.full_url, code, msg, hdrs, fp)

Python isn't really my preferred langage, so I don't know what to do. This is a script that's supposed to access my Gmail account and pull new mails from it. Do you guys have any suggestions? I'm using Arch Linux, if that helps.
Variant A:
Run this script as python3.4 /path/to/script
Variant B:
Change the schebang to #!/usr/bin/python3.4
use python 3.4 instead of python 3.5