Python API: should double type/[up|down]grade function registration raise an exception

[ssteinbach]

Following discussion from: #1387

The python binding for the registration system for types and up/downgrade functions currently returns a bool:

• OpenTimelineIO/src/py-opentimelineio/opentimelineio-bindings/otio_bindings.cpp

  Line 39 in 424967a

  TypeRegistry::instance().register_type(schema_name, schema_version,

• OpenTimelineIO/src/py-opentimelineio/opentimelineio-bindings/otio_bindings.cpp

  Line 54 in 424967a

  return TypeRegistry::instance().register_upgrade_function(schema_name, version_to_upgrade_to,

However, the bindings have a system for capturing these results and raising exceptions. I briefly experimented with this during the development of #1387, but it seems like the python unit tests assume that its ok to double register the same type without it triggering an exception.

For unit testing this probably means additional functions that allow un-registering types from the TypeRegistry.

I think the action items are:

• discuss at a TSC meeting whether this would be desired behavior,
  • ...and if so what exception should be raised