component AP gateway: properly close the HTTP connection on `checkSignature` exception: if something is going wrong during `checkSignature` (other than signature verification failing), a `500 Internal Server Error` code is returned, and the connection is properly closed.

from typing import Optional

from twisted.words.xish import domish


class BaseError(Exception):
    namespace: str
    condition: str
    text: Optional[str]
    textLang: Optional[str]
    appCondition: Optional[domish.Element]

class StanzaError(BaseError):
    ...