core (main): Let plugins have several handlers + various improvements: `get_handler` can now return several handlers, which is notably useful for component with several included services. Various improvements such move to `async` method, docstring/type hints update, and slight improvment of SatXMPPComponent. rel 453

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):
    ...