Some operators in Python have special names.
Many Pythonistas know about the notorious "walrus" operator (:=), but there are less famous
ones like the diamond operator (<>) — it's similar to the "not equals" operator but written in SQL style.
The diamond operator was suggested in PEP 401 as one of
the first actions of the new leader of the language Barry Warsaw after Guido went climbing Mount Everest.
Luckily, it was just an April Fool joke and the operator was never really a part of the language.
Yet, it's still available but hidden behind the "import from future" flag.

Usually you compare for non-equality using !=:

>>> "bdfl" != "flufl"
True

But if you enable the "Barry as FLUFL" feature the behavior changes:

>>> from __future__ import barry_as_FLUFL
>>> "bdfl" != "flufl"
  File "<stdin>", line 1
    "bdfl" != "flufl"
            ^
SyntaxError: with Barry as BDFL, use '<>' instead of '!='
>>> "bdfl" <> "flufl"
True

Unfortunately, this easter egg is only working in interactive mode (REPL), but not in usual *.py scripts.

By the way, it's interesting that this feature is marked as becoming mandatory in Python 4.0.