Validator class not found

    /**
     * @param  mixed    $value
     * @param  string   $classBaseName
     * @param  array    $args          OPTIONAL
     * @param  mixed    $namespaces    OPTIONAL
     * @return boolean
     * @throws Zend_Validate_Exception
     */
    public static function is($value, $classBaseName, array $args = array(), $namespaces = array())
    {
        $namespaces = array_merge((array) $namespaces, self::$_defaultNamespaces, array('Zend_Validate'));
        $className  = ucfirst($classBaseName);
        try {
            if (!class_exists($className, false)) {
                #require_once 'Zend/Loader.php';
                foreach($namespaces as $namespace) {
                    $class = $namespace . '_' . $className;
                    $file  = str_replace('_', DIRECTORY_SEPARATOR, $class) . '.php';
                    if (Zend_Loader::isReadable($file)) {
                        Zend_Loader::loadClass($class);
                        $className = $class;
                        break;
                    }
                }
            }

            $class = new ReflectionClass($className);
            if ($class->implementsInterface('Zend_Validate_Interface')) {
                if ($class->hasMethod('__construct')) {
                    $keys    = array_keys($args);
                    $numeric = false;
                    foreach($keys as $key) {
                        if (is_numeric($key)) {
                            $numeric = true;
                            break;
                        }
                    }

                    if ($numeric) {
                        $object = $class->newInstanceArgs($args);
                    } else {
                        $object = $class->newInstance($args);
                    }
                } else {
                    $object = $class->newInstance();
                }

                return $object->isValid($value);
            }
        } catch (Zend_Validate_Exception $ze) {
            // if there is an exception while validating throw it
            throw $ze;
        } catch (Exception $e) {
            // fallthrough and continue for missing validation classes
        }

        #require_once 'Zend/Validate/Exception.php';
        throw new Zend_Validate_Exception("Validate class not found from basename '$classBaseName'");
    }