trafaret.DataError's method as_dict returns either string or dict

[thenx]

Is that intended to be so or just some legacy code or smth? IMHO, it is:

1. Misguiding
2. Introduces necessity to validate and convert the result

Wouldn't it be better to always return dicts?

[Deepwalker]

Again this is a long time behaviour and definitely it need to be solved. Will think.

[thenx]

This also results in aiohttp_admin's exceptions during passing validation errors to frontend in util.py and mongo_utils.py (lines with **exc.as_dict())