Problem with inheritance and Config.fields

[samuelcolvin]

from pydantic import BaseModel


class Foo(BaseModel):
    a: int


class Bar(Foo):
    b: str

    class Config:
        fields = {
            'a': 'aaa',
            'b': 'bbb',
        }


print(Bar(aaa=1, bbb='s'))

Doesn't work.

1. should give explicit error if fields which aren't defined are referenced in Config.fields
2. should allow aliases for fields in inherited models.