Python 2.4, 2.5, and 3.1 are ancient history. Supporting them means not being able to use any reasonably modern python features (e.g. context managers...) and makes single source py2/3 support very difficult. Most of the rest of the python universe has dropped support for these old versions. We're doing it as well.

If you need to continue to use any of these python versions with MongoDB the 2.x branch of PyMongo will continue to be minimally maintained for some time.