问题：
MACOS安装scrapy时，安装lxml出现错误
In file included from src/lxml/lxml.etree.c:232:
/tmp/easy_install-O2UfP7/lxml-3.4.0/src/lxml/includes/etree_defs.h:14:10: fatal error: ‘libxml/xmlversion.h‘ file not found
#include "libxml/xmlversion.h"
^
1 error generated.
error: Setup script exited with error: command ‘cc‘ failed with exit status 1
解决方法：
xcode-select --install
fatal error: 'libxml/xmlversion.h' file not found
原文：http://www.cnblogs.com/skywter/p/3973672.html