If an exception is raised in this frame, the next three are used to
record the exception info (if any) originally in the thread state. See
comments before set_exc_info() -- it's not obvious.
Invariant: if _type is NULL, then so are _value and _traceback.
Desired invariant: all three are NULL, or all three are non-NULL. That
one isn't currently true, but "should be".
If an exception is raised in this frame, the next three are used to record the exception info (if any) originally in the thread state. See comments before set_exc_info() -- it's not obvious. Invariant: if _type is NULL, then so are _value and _traceback. Desired invariant: all three are NULL, or all three are non-NULL. That one isn't currently true, but "should be".