static unexpected(event, e) {
        // If you should ever get here, your app is definitely broken, and you need to fix
        // your event handler to prevent unhandled errors during event notifications.
        //
        // Console output is suppressed when running tests, to avoid polluting test output
        // with error messages that are intentional and of no value to the test.

        /* istanbul ignore if */
        if (!npm.main.suppressErrors) {
            const stack = e instanceof Error ? e.stack : new Error().stack;
            ColorConsole.error(`Unexpected error in '${event}' event handler.\n${stack}\n`);
        }
    }
@event unexpected
@param {string} event - unhandled event name.
@param {string|Error} e - unhandled error.
@private