Fix Python3 running error on Mac OS Catalina

(Just for my own reference)

Environment:

1.     macOS Catalina version 10.15.3

2.     Xcode 11.3.1

3.     Python3: 3.7.3

When tried to run python3 on macOS Catalina, got an error:

xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun

To fix this, run command “xcode-select –install”