Here is a simple implementation of a line-oriented reader deriving from a buffered reader.  Unlike the suggested extra derivation of buffered I/O class from a raw I/O class, my BufReader only wraps an "iterable" stream.  Besides, I found I had to return an empty string instead of None on EOF because Python2.5's codecs.py assumes the former.

Submitting this just in case it is found useful.