cli (base): new `a_quit` method to run async cleaning methods: it may be necessary to run some async cleaning method (e.g. if bridge is needed), this new method handles async cleaning method, and will be called when `SystemExit` is used, or if `a_quit` is called explicitely. rel 426

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):
    ...