While the original enum proposal, PEP 354, was rejected years ago, it keeps coming back up. Some kind of enum was intended to be added to 3.2, but it got pushed back to 3.3 and then forgotten. And now there's a PEP 435 intended for inclusion in Python 3.4. The reference implementation of PEP 435 is flufl.enum.
As of April 2013, there seems to be a general consensus that something should be added to the standard library in 3.4—as long as people can agree on what that "something" should be. That's the hard part. See the threads starting here and here, and a half dozen other threads in the early months of 2013.
Meanwhile, every time this comes up, a slew of new designs and implementations appear on PyPI, ActiveState, etc., so if you don't like the FLUFL design, try a PyPI search.