def get_plugin_class(self, plugin_name):
        """Returns the class registered under the given plugin name."""
        try:
            return self.plugin_classes[plugin_name]
        except KeyError:
            raise RezPluginError("Unrecognised %s plugin: '%s'"
                                 % (self.pretty_type_name, plugin_name))
Returns the class registered under the given plugin name.