Lib/test/crashers/losing_mro_ref.py does crash Python: _PyType_Lookup() borrows a reference to the type MRO, but the type MRO is replaced during the lookup. Python crashs because it reads an item from a tuple that was destroyed (in the specific test, it reads an item from a newly created tuple which is not the type MRO). Attached patch keeps a strong reference to the type MRO during the lookup to workaround this crasher. It fixes Lib/test/crashers/losing_mro_ref.py. If changing temporary has an impact on performances, a guard can be used to check that the type MRO has not been changed during the lookup.
