def validate(self, source):
    # Getting the value will raise an exception if it's in bad form.
    val = source.get(self.key, None)
    present = val is not None
    _ = self.get_value(val, present)
Raise an exception if this configuration value is missing but required,
dataset/ETHPy150Open cloudera/hue/desktop/core/src/desktop/lib/conf.py/Config.validate