vi ~/.muttrc
set smtp_oauth_refresh_command = "/usr/home/cpfong/bin/d.google/9NewOauth2.py --quiet\
        --user=my@gmail.com\
        --client_id=9530050.apps.googleusercontent.com\
        --client_secret=GOCSPX-xysysy\
        --refresh_token=1//0eh2gQlDkz02SCgYIA"

where:
---
user:		your google email
client_id:	login console.developer to get it	
client_secret:	login console.developer to get it	
refresh_token:	generate via ./oauth2.py like ./9NewOauth2.py --user=my@gmail.com --client_id=953005.apps.googleusercontent.com --client_secret=GOCSPX-xysysy --generate_oauth2_token

note: ./9NewOauth2.py --user xxx --generate_oauth2_token will return like this and Refresh Token is what i need
-----
Refresh Token: 1//0eh2gQlDkz02SCgYIA
Access Token: ya29.a0ARrdaM9p1E
Access Token Expiration Seconds: 3599

1 oauth2.py use client_id client_secret to generate a web link
2 and it ask you to get ret code from web link
3 input code and oath2.py stop and return refresh_token
4 use this refresh_token to goto next step