private function createDirectoryStructure() {
        foreach ($this->project->getNamespaces() as $namespace) {
            $namespaceDir = $this->dstDir . str_replace('\\', '/', $namespace->getFqsen());
            if (is_dir($namespaceDir)) {
                continue;
            }
            if (!mkdir($namespaceDir, 0755, true)) {
                throw new WriteException('Could not create directory ' . $namespaceDir);
            }
        }
    }