given:
        TransformErrorHandler handler = handler()
        def className = "some/Class"

        when:
        handler.enterClassLoadingScope(className)
        handler.classLoadingError(className, new IOException("I/O"))
        handler.exitClassLoadingScope()

        then:
        def e = thrown(ClassNotFoundException)
        e.cause instanceof IOException

 *     }
 *     handler.exitClassLoadingScope();
 *     return result;
 * }
 *
 * public void transformFailed(String className, Throwable th) {
 *     handler.classLoadingError(className, th);
 * }
 * </code>
 * </pre>
 * <p>
 * This class is thread-safe, though it only tracks pending exceptions per-thread.
 */
public class TransformErrorHandler {

            return replacer.getInstrumentedClass(className, protectionDomain);
        }

        @Override
        public void transformFailed(@Nullable String className, Throwable cause) {
            errorHandler.classLoadingError(className, cause);
        }

        @Override
        protected Class<?> findClass(String name) throws ClassNotFoundException {
            errorHandler.enterClassLoadingScope(name);

            return replacer.getInstrumentedClass(className, protectionDomain);
        }

        @Override
        public void transformFailed(@Nullable String className, Throwable cause) {
            errorHandler.classLoadingError(className, cause);
        }

        @Override
        protected Class<?> findClass(String name) throws ClassNotFoundException {
            errorHandler.enterClassLoadingScope(name);