TBH I think the main thing about that release, for me, was the introduction of context managers ("with"). I don't remember any particular breakage but I wasn't doing sysadmin at the time, maybe there is something in the bowels of redhat that relied on some broken behaviour...

I never understood the point of hiring a full team for at least 6 months just for that. The only explanation I can find is that the project manager was clueless about Python.