Python 3
from urllib.error import HTTPError
Python 2
from urllib2 import HTTPError
Just catch HTTPError, handle it, and if it's not Error 404, simply use raise to re-raise the exception.
See the Python tutorial.
e.g. complete example for Pyhton 2
import urllib2
from urllib2 import HTTPError
try:
urllib2.urlopen("some url")
except HTTPError as err:
if err.code == 404:
<whatever>
else:
raise