Error message:

error: Microsoft Visual C++ 14.0 is required. Get it with “Microsoft Visual C++ Build 		Tools”: http://landinghub.visualstudio.com/visual-cpp-build-tools

Solution

# Open the link to download the whl file for the corresponding version of twisted The version I downloaded is Twisted-17.9.0-cp36-cp36m-win_amd64.whl (cp followed by python version, amd64 stands for 64-bit)
http://www.lfd.uci.edu/~gohlke/pythonlibs/#twisted  

# After downloading, execute the following command. 
python -m pip install E:\Twisted-17.9.0-cp36-cp36m-win_amd64.whl 

# Run with the following error. 
Twisted-17.9.0-cp36-cp36m-win_amd64.whl is not a supported wheel on this platform.

# After changing to another version of Twisted-17.9.0-cp36-cp36m-win32.whl, execute the following command. 
python -m pip install E:\Twisted-17.9.0-cp36-cp36m-win32.whl 

# After executing the previous command, the following message indicates that Twisted is successfully installed 
Successfully installed Twisted-17.9.0 

# Then execute the following command.
python -m pip install scrapy 

This time, it can be installed successfully