python安装scrapy爬虫框架，提示 error: command 'clang' failed with exit status 1

scrapy是python爬虫中，比较常用的一种框架。

提示异常：

Mac上安装的时候，报错"error: command 'clang' failed with exit status 1"。

songrenqingdeMacBook-Pro:~ songrenqing$ pip install scrapy
Collecting scrapy
  Using cached https://files.pythonhosted.org/packages/db/9c/cb15b2dc6003a805afd21b9b396e0e965800765b51da72fe17cf340b9be2/Scrapy-1.5.0-py2.py3-none-any.whl
...
    xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun
    error: command 'clang' failed with exit status 1

异常原因：

Mac的OSX系统的C语言，编译器用的是Clang。既然报错与clang有关，应该是xcode command tools出现问题，网上搜了一下其它文章，大部分人也都是通过更新安装xcode解决的。

songrenqingdeMacBook-Pro:~ songrenqing$ gcc --version
Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 9.1.0 (clang-902.0.39.2)

解决办法：

执行 xcode-select --install 命令后，重新安装 

songrenqingdeMacBook-Pro:~ songrenqing$ xcode-select --install
xcode-select: note: install requested for command line developer tools
songrenqingdeMacBook-Pro:~ songrenqing$ pip install scrapy
......
Successfully installed Twisted-18.4.0 scrapy-1.5.0