Add 'NagException' to disclose plugin fail

src/main/java/org/bukkit/plugin/AuthorNagException.java

@@ -0,0 +1,20 @@
+package org.bukkit.plugin;
+
+public class AuthorNagException extends RuntimeException {
+    private final String message;
+
+    /**
+     * Constructs a new UnknownDependencyException based on the given Exception
+     *
+     * @param message Brief message explaining the cause of the exception
+     * @param throwable Exception that triggered this Exception
+     */
+    public AuthorNagException(final String message) {
+        this.message = message;
+    }
+
+    @Override
+    public String getMessage() {
+        return message;
+    }
+}