Enhancer print error exception.

core/src/main/java/com/taobao/arthas/core/advisor/Enhancer.java

@@ -114,7 +114,7 @@ public class Enhancer implements ClassFileTransformer {
                 }
             } catch (Throwable e) {
                 logger.error("the classloader can not load SpyAPI, ignore it. classloader: {}, className: {}",
-                        inClassLoader.getClass().getName(), className);
+                        inClassLoader.getClass().getName(), className, e);
                 return null;
             }