显然我需要安装 Xcode 命令行工具.(即使你已经安装了 Xcode.)我有最新的 Xcode 测试版，但我仍然需要安装命令行工具.

Apparently I needed to install the Xcode command line tools. (Even if you have Xcode installed.) I have the latest beta of Xcode, but I still needed to install the command line tools.

xcode-select --install

然后运行 ​​pip install scrapy 工作正常.

And then running pip install scrapy worked fine.