Nick Coghlan added the comment:
Also clarifying a point that came up later in the thread [1]: one of the
motivating examples that came up in the thread was the idea of using this to
catch AttributeError exceptions in property and __getattr__ implementations and
convert them to RuntimeError.
New submission from Steven D'Aprano:
As discussed on Python-Ideas, there's some interest in a context manager that
can convert an exception from one type to another (similarly to the way PEP 479
has StopIteration converted to RuntimeError.
See the thread starting here:
