新手刚学 Flask，在 pycharm 下敲代码，现在到 E-mail 章无法运行？

D:\Python 3.6\lib\site-packages\flask_sqlalchemy\__init__.py:800: UserWarning: SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead ad will be disabled by default in the future. Set it to True to suppress this warning. warnings.warn('SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and will be disabled by default in the future. Set it to True to suppress this warning.') usage: hello.py [-?] {shell,db,runserver} ... positional arguments: {shell,db,runserver} shell Runs a Python shell inside Flask application context. db Perform database migrations runserver Runs the Flask development server i.e. app.run() optional arguments: -?, --help show this help message and exit Process finished with exit code 2 

有提到需要设置环境变量，但是在 mintty 下设置也报错 无论是

export MAIL_USERNAME=<mail username>或者 set MAIL_USERNAME=<mail username>

报错

bash: syntax error near unexpected tokennewline

我看书是不是漏了啥？

环境变量的设置有没有办法建立临时的？不更改 windows 系统的全局环境变量？ 谢谢各位帮助，祝大家新年快乐！