I should have changed the Versions sooner, as soon as it became obvious that this was not just a 3.4 issue. The 'temporary' 3.4-only patch breaks forward merging of a better patch. I will back it out just before I commit a 3.3 patch to both eliminate the .formatwarning replacement (#18242) and move the .showwarning replacement (part of Victor's patch).

If we ever add tests of PyShell.main and run.main (which we should), the problem of this issue will recur unless we make *sure* that the monkey patch moved inside those functions is reverted. Will try: finally: do that? I will leave this for a second patch.