[labawi]

Note that I am not against using python in mission-critical code.

I was referring to untestable code with a myriad of edge-cases, in which case you have a problem that will surface sooner or later, be it 2to3 transition or something else.

If the code is truly static, you can ignore the transition and deprecation. Otherwise you should probably work on documentation/testing/refactoring and/or porting to another language.

2to3 transition was handled badly, up to about 2.7 and 3.4 or so, but the pains described here seem mostly self-inflicted, and I don't see it as an argument against the needed changes.