T115269 means that
in addition to
"datavalue":{ "value":{ "amount":"+700", "unit":"1", "upperBound":"+710", "lowerBound":"+690" }, "type":"quantity" },
clients may now also encounter this:
"datavalue":{ "value":{ "amount":"+700", "unit":"1" }, "type":"quantity" },
WbQuantity should both be able to handle this and we should ensure that we don't add errors unless they are explicitly set.
Before deploying this should be announced on the mailing list as some users may rely on the current error=None -> +/-0 "feature".