Sure, we have tests, we have a whole ecosystem -- written in python2 -- but that's not a justification to introduce breaking changes or a guarantee that the tes

Sure, we have tests, we have a whole ecosystem -- written in python2 -- but that's not a justification to introduce breaking changes or a guarantee that the tests will catch all regressions. We also have dependencies. Moreover, unless your system is a toy, tests aren't going to give you the same guarantees as having a system be hammered by real world events for 5 years.