Retry on failure to retrieve requested data, else return proper class

[adamhsparks]

@jonocarroll wrote in another issue,,

A common technique would be retry on fail. As for how to test a function which may fail, I'd like to avoid the popular route of 'just don't test'. With proper error-handling the function could return something of the appropriate class, even if it's empty.

Implement this idea for bomrang functions retrieving data from BOM servers that may not properly respond.