Segfault when cursing a class method that already exists as instance method on python3 objects

[clarete]

The test case: f5c25ba3a865c939ee0bab1f12b43eba47b87167

It's unlikely that it will blow up in the first call. Actually, to see this bug happening, I'm running this command:

while :; do make; done   # :(

Thanks Mr. @spulec for reporting this issue with a nice test case!