在使用$ pip install scrapy,命令来安装scrapy时，cmd界面提示红色信息
（Command "c:\users\kadsm\appdata\local\programs\python\python37\python.exe -u -c "import setuptools, tokenize;__file__='C:\\Users\\kadsm\\AppData\\Local\\Temp\\pip-install-gn1i0shv\\Twisted\\setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record C:\Users\kadsm\AppData\Local\Temp\pip-record-dqtyfczg\install-record.txt --single-version-externally-managed --compile" failed with error code 1 in C:\Users\kadsm\AppData\Local\Temp\pip-install-gn1i0shv\Twisted\）
并且该提上上边还有个错误提示
（error: Microsoft Visual C++ 14.0 is required. Get it with “Microsoft Visual C++ Build Tools”: http://landinghub.visualstudio.com/visual-cpp-build-tools
）
这时候请安装Microsoft Visual C++ Build Tools
下载页面：https://blogs.msdn.microsoft.com/pythonengineering/2016/04/11/unable-to-find-vcvarsall-bat/
也可以直接使用下载地址：
https://download.microsoft.com/download/5/f/7/5f7acaeb-8363-451f-9425-68a90f98b238/visualcppbuildtools_full.exe
错误提示如下图：
