def validate_username(self, username):
        if not self.username_regex:
            return True
        return bool(self.username_regex.match(username))
Hijack to ignore the absence of a CAP command.
dataset/ETHPy150Open jupyterhub/jupyterhub/jupyterhub/auth.py/Authenticator.validate_username--crossover with--dataset/ETHPy150Open Shizmob/pydle/pydle/features/ircv3/cap.py/CapabilityNegotiationSupport.on_raw_451