- Run the tests in python 2. Did they work? If not, quit this project and do another one.
- Run the tests in python 3. Did they work? If so, you're actually done. This one needs to be marked as "good to go".
- Run python-modernize.
- Run the tests in python 2. Do they work?
- Run the tests in python 3. Do they work?
- If the above fails, you might try running 3to2 which will make a python3-only version. This is acceptable, but less desirable.
- No matter what kind of success you get, make sure to report it all to the upstream in the form of a ticket on their bugtracker. Even if you didn't get it to work, the stuff you find out is valuable.