Run an existing script using its description to look it up
        
        Usage: C{engine.run_script(description)}
        
        @param description: description of the script to run
        @raise Exception: if the specified script does not exist

def run_script(self, description):
        """
        Run an existing script using its description to look it up
        
        Usage: C{engine.run_script(description)}
        
        @param description: description of the script to run
        @raise Exception: if the specified script does not exist
        """
        targetScript = None
        for item in self.configManager.allItems:
            if item.description == description and isinstance(item, model.Script):
                targetScript = item

        if targetScript is not None:
            self.runner.run_subscript(targetScript)
        else:
            raise Exception("No script with description '%s' found" % description)