I once spent a week porting some python2 researchware into python3. It was only at the end of that week that I discovered that it was the actual logic of the researchware that was broken, and not the way I was porting it. I now distrust all FOSS except for widely used and tested ones. You would think that a graduate student would debug (or at least fix to the point of being interpretable) the work that they spent months on before publishing it as finished and adding it to pip.

And yes, 2to3 fixes 90% of porting problems. But in my experience, it was especially bad at handling, of all things, import statements. Definitely not a silver bullet.