import { SimpleAppConfigError } from './simpleAppConfigError';
/**
 * An error extending {@link SimpleAppConfigError} that should be thrown when accessing an environment variable that is undefined.
 */
export declare class UndefinedEnvVarError extends SimpleAppConfigError {
    /**
     * Constructor for {@link UndefinedEnvVarError}.
     * @param key The key of the environment variable that is undefined.
     */
    constructor(key: string);
}