Python 3 preparation: HTTP headers handling in roundup_server.py. HTTP headers are handled differently in Python 3 (where they use email.message.Message) compared to Python 2 (where they use mimetools.Message). In some places the code needs to check which version of the interface is available. For the common case of getting a single header, ".get" is available in both versions, and is an alias of ".getheader" in Python 2. (Note that the Python 3 semantics of ".get" are slightly different from those in Python 2 if there is more than one of a given header - it returns an arbitrary one, when in Python 2 it's specified to return the last one. Hopefully the places using this interface rather than explicitly allowing for multiple headers with the same name are OK with that and it shouldn't actually occur with well-behaved clients.)