There's already a `error.py` module right next to this, which deals with much the same.

Can you merge those? I actually like the plural spelling errors.py better. There's already a JSONError in the error module, which is specific to the search/submit API's. Maybe create a GeoJSONError for the geolocate/geosubmit API's to distinguish it. Going forward I want to deprecate the search/submit APIs at some point, so the geo* stuff can become the default arguments, for example in the preprocess_request function.