cli: `call` command: This command has 2 subcommands: `make` and `receive` to make a new call or wait for one. When call is in progress, a window will be created to show incoming stream and local feedback, and a text UI is available to (un)mute audio or video, and hang up. 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):
    ...