'Constructs a new XMPP Message from an HTTP request.
Args:
vars: A dict-like object to extract message arguments from.'

def __init__(self, vars):

    try:
        self.__sender = vars['from']
        self.__to = vars['to']
        self.__body = vars['body']
    except KeyError as e:
        raise InvalidMessageError(e[0])
    self.__command = None
    self.__arg = None
