flask-login-0.2.7 works with python-3.3. Only change needed is to add 3_3 to PYTHON_COMPAT.
Is there a reason, why this simple change does not get applied and flask-login is still py2-only in tree, even though it got bumped several times?
Because not everyone refers to bugs while bumping. It just happens. I've fixed this for 0.2.11, thanks for reporting and the ping.