AttributeError: 'NoneType' object has no attribute 'drivername'

[ellierui]

[root@wisdom-c flask-rest-api-master]# echo 'db.create_all()' | ./manage.py shell
/usr/lib64/python2.7/site-packages/flask_sqlalchemy/init.py:794: FSADeprecationWarning: SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and will be disabled by default in the future. Set it to True or False to suppress this warning.
'SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and '

Traceback (most recent call last):
File "", line 1, in
File "/usr/lib64/python2.7/site-packages/flask_sqlalchemy/init.py", line 963, in create_all
self._execute_for_all_tables(app, bind, 'create_all')
File "/usr/lib64/python2.7/site-packages/flask_sqlalchemy/init.py", line 955, in _execute_for_all_tables
op(bind=self.get_engine(app, bind), **extra)
File "/usr/lib64/python2.7/site-packages/flask_sqlalchemy/init.py", line 896, in get_engine
return connector.get_engine()
File "/usr/lib64/python2.7/site-packages/flask_sqlalchemy/init.py", line 556, in get_engine
self._sa.apply_driver_hacks(self._app, info, options)
File "/usr/lib64/python2.7/site-packages/flask_sqlalchemy/init.py", line 830, in apply_driver_hacks
if info.drivername.startswith('mysql'):
AttributeError: 'NoneType' object has no attribute 'drivername'

[chairus]

What's the value of the environment variable DATABASE_URL?