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# Revision $Id: validators.py 11729 2010-10-23 21:21:54Z kwc $

"""Internal-use Python decorators for parameter validation"""

class ParameterInvalid(Exception):
    """Exception that is raised when a parameter fails validation checks"""
    def __init__(self, message):
        self._message = message

    def __str__(self):
        return str(self._message)

def non_empty(param_name):
    """Validator that checks that parameter is not empty"""
    def validator(param, context):
        if not param:
            raise ParameterInvalid("ERROR: parameter [%s] must be specified and non-empty"%param_name)
        return param
    return validator
