I've used this module for upgrading a python2-only lib : https://pypi.python.org/pypi/future . Basically it allow you to write Python 3 code that will run on Python 2 interpreter (bar from using advanced features like coroutine or matrix mult operator).

Once you decide not to support Python2 anymore, just drop the imports. They also have a Py2/3 compat cheet sheet : http://python-future.org/compatible_idioms.pdf