Investigate and possibly replace threading RLock in ObjectAggregator

[ormsbee]

I'm not sure if this is async safe, or if everything happens up front at startup anyway:

XBlock/xblock/runtime.py

Lines 1189 to 1226 in 77bfe4d

	class ObjectAggregator:
	"""
	Provides a single object interface that combines many smaller objects.
	Attribute access on the aggregate object acts on the first sub-object
	that has that attribute.
	"""
	def __init__(self, *objects):
	self.__dict__['_objects'] = objects
	def _object_with_attr(self, name):
	"""
	Returns the first object that has the attribute `name`
	:param name: the attribute to filter by
	:type name: `str`
	:raises AttributeError: when no object has the named attribute
	"""
	for obj in self._objects:
	if hasattr(obj, name):
	return obj
	raise AttributeError(f"No object has attribute {name!r}")
	def __getattr__(self, name):
	return getattr(self._object_with_attr(name), name)
	def __setattr__(self, name, value):
	setattr(self._object_with_attr(name), name, value)
	def __delattr__(self, name):
	delattr(self._object_with_attr(name), name)
	# Cache of Mixologist generated classes
	_CLASS_CACHE = {}
	_CLASS_CACHE_LOCK = threading.RLock()

We need to make it async-safe for ASGI style deployments.

Open question: Is this used anywhere at all? It looks like it might no longer be called anywhere other than its own tests.