Ability for scraper to push errors down the pipeline without throwing about li

[lazd]

@qgolsteyn @ryanblock thoughts?

[jzohrab]

What's an example of when this would be useful?

To me, idea 1 errors array isn't bad, it's a collector parameter. Have used such things in the past. Could even be a stream or a logger they push to.

• Other possibility: global logging, potentially. Scrapers could instantiate a ScraperError(this, err) and give it to a global logger routine. If scrapers know they can continue despite the error, great.