How is it a failure? When they were talking about Python 3 at PyCon 2008 and 2009, it was expected that the migration would take this long. Folks knew migrating would be long and hard, and that the approach would need to be revised.

It's only relatively recently that Python 3 passed a certain threshold that made deprecation of Python 2 something that could actually be executed upon. Had the growth been slower in the last five years I think the timeline would have been different.

If I was going to critique Python "failures" I think the bigger target for me would be the integration of async concepts into the platform and language. This could have been handled more smoothly and with better community cohesion, but most HNers only have a superficial understanding, i.e the GIL is bad and Python can't compete with Go.