python - 尝试运行 Scrapy Dmoz 演示代码时出现 libxml2 或 lxml 错误

Question

File "/root/my_new_env/lib/python2.6/site-packages/scrapy/selector/dummysel.py", line 16, in _raise
    raise RuntimeError("No selectors backend available. " \
exceptions.RuntimeError: No selectors backend available. Please install libxml2 or lxml

我安装了 libxml2 和 lxml。任何想法为什么我会收到这个错误？