site.py内置阴影

site.py shadows built-in site module.

由于导入了错误的site.py模块，所以从未设置用于搜索用户安装的软件包的路径，因此解释器无法找到bs4模块.

Due to wrong site.py module being imported, paths used to search for user-installed packages are never set, therefore interpreter is unable to find bs4 module.