Better debugging for DB Cache path

system/database/DB_cache.php

@@ -95,12 +95,22 @@ public function check_path($path = '')
 			? rtrim(realpath($path), DIRECTORY_SEPARATOR).DIRECTORY_SEPARATOR
 			: rtrim($path, '/').'/';
 
-		if ( ! is_dir($path) OR ! is_really_writable($path))
+		if ( ! is_dir($path))
 		{
+			log_message('debug', 'Cache Path Error: '.$path);
+
 			// If the path is wrong we'll turn off caching
 			return $this->db->cache_off();
 		}
 
+		if ( ! is_really_writable($path))
+		{
+			log_message('debug', 'Cache Dir Not Writable: '.$path);
+
+			// If the path is not really writable we'll turn off caching
+			return $this->db->cache_off();
+		}
+
 		$this->db->cachedir = $path;
 		return TRUE;
 	}