Do not return generator when DocumentHandler is DOCUMENT

[jbrown299]

    with open('cached-microdesc-consensus', 'rb') as consensus_file:
        network_status = parse_file(consensus_file,
                                    'network-status-microdesc-consensus-3 1.0',
                                    document_handler=DocumentHandler.DOCUMENT,
                                    validate=True)

So here is parse_file always return generator. In my opinion will be better if we parse as single document return object but not generator.

Or you mean it is possible to load several documents from one file?

[atagar]

Hi James. You're right that this is a common gotcha, please use next...

network_status = next(parse_file(...))

Some files contain a single descriptor, whereas others have multiple. Varying our return type based on the context would make this function even more confusing to use.