private function findClassFile($class)
    {
        list($classpath, $classname) = $this->findClasspathAndClass($class);
        $classpath .= str_replace('_', DIRECTORY_SEPARATOR, $classname) . '.php';

        foreach ($this->autoloader->getPrefixes() as $prefix => $dirs) {
            if (0 === strpos($class, $prefix)) {
                return current($dirs) . DIRECTORY_SEPARATOR . $classpath;
            }
        }

        if ($dirs = $this->autoloader->getFallbackDirs()) {
            return current($dirs) . DIRECTORY_SEPARATOR . $classpath;
        }

        throw new ContextNotFoundException(sprintf(
            'Could not find where to put "%s" class. Have you configured autoloader properly?',
            $class
        ), $class);
    }