Is it normal that even after the call to next(), the generator frame contains a reference to the RuntimeError?

Long explanation:
- When the function exits, there is a cycle [parent frame]-> ['it' variable]-> [generator frame]-> [RuntimeError]-> [parent frame].
- gc.collect() collects them all, destroys the generator, this causes GeneratorExit exception to be sent into the generator frame.
- This executes SWAP_EXC_STATE() in ceval.c ("/* We were in an except handler when we left, restore the exception state which was put aside */"), this *moves* the reference to the exception from the frame to the thread state.
- The exception is resurrected, but this does not prevent the gc from calling its tp_clear method! and setting exc_info() as a side-effect of gc.collect() is really weird...