Request:
'https://www.googleapis.com/oauth2/v4/token'
{'headers': {'User-Agent': 'python-keystoneclient'}, 'allow_redirects': False, 'data': {'username': 'vinc.devl.test@gmail.com', 'scope': 'openid email profile', 'password': 'XXX', 'grant_type': 'password'}, 'auth': ('XXX.apps.googleusercontent.com', 'XXX'), 'verify': False}

Response:
Code: 400
u'{
 "error": "invalid_request",
 "error_description": "Invalid OAuth 2 grant type: PASSWORD"
}
'