I like how you picked an example that is explicitly not TCO-able. In any case, this particular problem is no longer an issue as of Python 3.6, as that now coll

I like how you picked an example that is explicitly not TCO-able. In any case, this particular problem is no longer an issue as of Python 3.6, as that now collapses repeated stacktrace lines (see https://bugs.python.org/issue26823 https://bugs.python.org/issue26823). Although this doesn't work for mutual tail calls, it does solve the debug noise issue in the most common case.