Index: wp-includes/classes.php
===================================================================
--- wp-includes/classes.php	(revision 3657)
+++ wp-includes/classes.php	(working copy)
@@ -339,4 +339,55 @@
 	}
 }
 
+class WP_Error {
+	var $errors = array();
+
+	function IXR_Error($code = '', $message = '') {
+		if ( ! empty($code) )
+			$this->errors[$code][] = $message;
+	}
+
+	function get_error_codes() {
+		if ( empty($this->errors) )
+			return array();
+
+		return array_keys($this->errors);
+	}
+
+	function get_error_code() {
+		$codes = $this->get_error_codes();
+
+		if ( empty($codes) )
+			return '';
+
+		return $codes[0];	
+	}
+
+	function get_error_messages($code) {
+		if ( isset($this->errors[$code]) )
+			return $this->errors[$code];
+		else
+			return array();	
+	}
+
+	function get_error_message($code = '') {
+		if ( empty($code) )
+			$code = $this->get_error_code();
+		$messages = $this->get_error_messages($code);
+		if ( empty($messages) )
+			return '';
+		return $messages[0];
+	}
+
+	function add($code, $message) {
+		$this->errors[$code][] = $message;	
+	}
+}
+
+function is_wp_error($thing) {
+	if ( is_object($thing) && is_a($thing, 'WP_Error') )
+		return true;
+	return false;
+}
+
 ?>